Observing Programmes: Cosmology
Round 1 (24)
Round 2 (56)
HerMES is the Herschel Multi-tiered Extragalactic Survey, an astronomical project to study the evolution of galaxies in the distant Universe. It is the largest project on ESA's Herschel Space Observatory. HerMES maps large regions of the sky using cameras that are sensitive to infrared radiation. We expect to discover over 100 thousand galaxies. The light from most of these galaxies will have taken more than 10 billion years to reach us, which means we will see them as they were 3 or 4 billion years after the big bang. Since the cameras are detecting infrared radiation they see star formation that is hidden from conventional telescopes. We expect that our cameras will catch many of the galaxies at the moment they are forming most of their stars.
Lead Scientist: Seb Oliver (University of Sussex)
Observations of some of the most distant quasars in the far-infrared shows that a substantial amount of dust was created in the first billion years after the Big Bang. However, the wavelengths observed to date haven't been able see the bulk of the emission, which is now possible using SPIRE and PACS. By observing over 100 of the most distant quasars it is possible to analyse their properties. In addition, PACS spectroscopy of four of the brightest quasars will allow the different origins of the far-infrared emission to be disentangled.
Lead Scientist: Klaus Meisenheimer (Max-Planck-Institut für Astronomie)
PEP, the PACS Evolutionary Probe is a Herschel guaranteed time key programme survey of the extragalactic sky, aimed to study the restframe far-infrared emission of galaxies in the past 11 billion years (up to redshifts of about 3) as a function of environment. The survey will shed new light on the constituents of the cosmic IR background and their nature, as well as on the co-evolution of AGN and starbursts. PEP is coordinated with SPIRE observations of the same fields in the HerMES program.
Lead Scientist: Dieter Lutz (Max Planck Institut für Extraterrestrische Physik)
By imaging 8 galaxy clusters seen as they were 7-11 billion years ago, this project will measure the star-formation history of clusters in this previously unexpored period of cluster evolution. The clusters have a range of sizes and contain a wide distribution of galaxy types. This should confirm an effect detected with Spitzer, where the number of star-forming galaxies increased over this period. It should also shed some light on the history of galaxy clusters we see in the local Universe.
Lead Scientist: Bruno Altieri (ESAC)
Galaxies which are bright at Ultraviolet wavelengths are a key population of galaxies in the distant Universe, and are essential for understanding the history of star formation and the assembly of galaxies. However, initial Herschel results indicate that they behave differently to similar galaxies in the nearby (and therefore recent) Universe. To understand the discrepancy, this project will focus on 16 galaxies which are gravitationally lensed. The gravity of much closer galaxies, or even massive galaxy clusters, causes the path of light to be bent, magnifying the images of the distant galaxies and allowing them to be studied in much more detail.
Lead Scientist: Dieter Lutz (Max Planck Institut für Extraterrestrische Physik)
A direct probe into the Epoch of Reionisation: Herschel's first look at high z GRB host, the case for GRB 050904
The early Universe was largely made of neutral gas, but at some point in the first billion years the gas was "reionised" by the first stars and galaxies, in a period know as the "Epoch of Reionisation". The role of galaxies in this is not completely understood, however, and are very difficult to study at such large distances. Gamma Ray Bursts (GRB) are exceptionally bright explosions which occur when very massive stars die, and are critically important in understanding star formation in the very early Universe. The galaxy which is home to one particular GRB, discovered in 2005, has been studied extensively by Hubble and Spitzer and optical and mid-infrared wavelengths, and is known to lie in the distant Universe. By observing the galaxy in the far-infrared with PACS and SPIRE, the physical properties of the galaxy could be revealed. This will directly probe the epoch of reionisation, and help understand how galaxies in the very early Universe differed from those we see much closer to us.
Lead Scientist: José María Castro Cerón (ESAC)
The galaxy known as IRAS 08339+6517 is a peculiar object, discovered independently by IRAS in the far-infrared and also at optical wavelengths. The strong emission from hydrogen, oxygen, carbon, nitrogen and silicon, combined with its brightness at X-ray wavelengths, suggests that it may be a "starburst galaxy", with a very high rate of star formation, and at the same time contain a very active core. By obtaining the first far-infrared spectrum of this remarkable object, the physical conditions of the gas and dust in the galaxy will be determined.
Lead Scientist: Martin Harwit (Cornell University)
We propose a unique addition to the HerMES family of maps, the HerMES Large Mode Survey (HeLMS), which will be observed as part of the remaining SPIRE GT time. The field covers 270 deg2 with two repeats over roughly 106 hours. It is chosen to overlap the SDSS Stripe 82 in a region where the Galactic cirrus with a mean flux density of ~1.2 MJy/sr is at its lowest. The ancillary coverage in this field is extensive, particularly in the optical, making it an attractive large field. The scientific advantages of having a field with the size and makeup of HeLMS are twofold: first, the large survey area, of which ~55 deg2 overlaps Stripe 82, will allow us to resolve approximately ~250,000 sources, of which ~250-500 will be gravitationally lensed. Second, the large, uniform and cross-linked area will allow for unprecedented measurement of large-scale modes (down to l ~ 150). Such fidelity would be a unique asset in the submillimeter regime for the foreseeable future, and would enable cross-frequency correlation analysis with ~80 deg2 of deep ACT maps, Planck over the full 270 deg2, as well as future observations with upcoming instruments like ALMA, ACTpol, and others.
Lead Scientist: Marco Viero
Allocated time: 103.4 hours
The Herschel ATLAS is the largest Herschel survey and will survey 550 square degrees of sky in five far-infrared and submillimetre bands, which is one eightieth of the sky and four times larger than all the other Herschel extragalactic surveys combined. There are five main science programmes, the principal one being a survey of the dust in 50,000 nearby galaxies. This follows on from the highly successful Sloan Digital Sky Survey, an optical survey that surveyed hundreds of thousands of galaxies in the nearby universe. However, Sloan missed the stars that are hidden by dust and didn't tell us anything about the gas in the galaixes out of which the stars form. H-ATLAS will do both of these.
Lead Scientists: Steve Eales (Cardiff University), Loretta Dunne (University of Nottingham)
The GOODS fields are regions of the sky which have been observed at a huge range of wavelengths by many of the greatest space observatories, including Hubble, Chandra and Spitzer. By observing a small area of sky with PACS the project can detect some of the faintest objects, and detect galaxies in the earliest stages of the Universe.
Lead Scientists: David Elbaz (CEA Saclay)
UK contact: Dave Alexander (University of Durham), Rob Ivison (UK Astronomy Technology Centre)
Initial Herschel results have demonstrated the power of the observatory for characterizing the properties of ultraluminous, star-forming galaxies during the peak era of star formation. Even with Herschel; however, the only way to spectroscopically study the properties of more typical, lower luminosity systems is by using gravitational lensing to augment the capability of the telescope. We request 12.8 hrs to obtain PACS and HIFI spectroscopy for a single, exceptionally magnified luminous infrared galaxy at z=2.791 that is lensed by the Bullet Cluster. This system, a dusty luminous infrared galaxy, is magnified by a factor of 100 and has a star-formation rate of 100 solar masses per year. It is the lowest stellar mass, lowest intrinsic luminosity galaxy known at z>2 that is magnified sufficiently to enable Herschel spectroscopy, providing our best chance of studying in detail a typical star-forming galaxy at this epoch. The primary goals with the current observations are (1) to obtain a high-fidelity determination of the warm gas mass in this sytem via molecular hydrogen rotational lines, and (2) to constrain the properties of the HII and photodissociation regions via fine structure lines, including the [CII] cooling line. The global objective is to obtain a detailed view of the ISM in this galaxy -- which is likely to yield the best information that we will have for any low mass galaxy at this epoch.
Lead Scientist: Anthony Gonzalez
Allocated time: 12.8 hours
Recent observations suggest a reversal in the star formation rate density relation at z>1 such that the average star formation rate in galaxies increases with increasing local galaxy density; the epoch at which this transition occurs is poorly constrained. Two high redshift clusters have shown an increased fraction of actively star forming galaxies towards the center of the cluster, albeit with small number statistics. We propose a statistical study of the dust-obscured star formation activity in a mass limited sample of 12 clusters from z=1.1-1.8 with PACS imaging at 100/160 microns. With 54.7 hours of observing time, we will detect ~150 cluster galaxies down to 100 solar masses per year and many more field galaxies. Our sample spans the fundamental redshift range during which massive clusters show signs of transitioning from a stage of active formation to passive evolution. We will determine the role of the cluster environment on the evolution of infrared luminous galaxies as a function of redshift. These Herschel observations will allow us to map out the star formation activity in galaxy clusters and constrain their mass assembly epoch.
Lead Scientist: Alexandra Pope
Allocated time: 54.7 hours
Early results from Herschel have shown we are entering a new and exciting era in the study of the interstellar media of galaxies. Using the far-infrared cooling lines, we have demonstrated the capability of the PACS spectrometer in deep integrations reaching line sensitivities of 3 sigma sensitivities of 3e-18 W/m/m in <~2 hours exposures on resolved lines, reaching as low as 1e-18 W/m/m in ~7 hours with the red detector allowing us to probe the ISM of galaxies in place at the peak of star-formation and AGN activity in the Universe (Sturm et al. 2010). This proposal builds on these first studies by performing PACS spectroscopy of a sample of bright and strongly lensed infrared/sub-mm galaxies at moderate to high redshift. By virtue of the magnification due to lensing we are able to probe intrinsically lower luminosity galaxies which would normally be beyond the reach of the Herschel spectro- meters, and, for the first time, constrain the physical processes and state of the ISM in these high-redshift galaxies.
Lead Scientist: Aprajita Verma
Allocated time: 77.3 hours
We propose to make deep PACS observations of a 1.75-square degree region of the Coma cluster which encompasses both the dense core and the southwest infall region, and covers a factor of 100 in galaxy density. In combination with SPIRE data from the Herschel-ATLAS Key Project, these data will provide the first reliable measurements of the dust properties in a rich galaxy cluster. We have assembled a vast multi-wavelength dataset over this region of Coma that has allowed us to compute reliable stellar masses for nearly 2,000 spectroscopically-confirmed cluster members. We will (i) measure the far-infrared luminosity function and determine whether the turnover seen in Virgo is also present in Coma; (ii) measure the dust masses and temperatures of all galaxies brighter than this turnover; (iii) derive reliable *total* star-formation rates for all galaxies from a combination of UV, H-alpha, and far-IR imaging, and hence address the controversy surrounding optically-classified "post-starburst" galaxies; (iv) relate these important properties of the cluster galaxies to quantities such as stellar mass, galaxy morphology, local galaxy density, and the density of the intra-cluster medium, to determine which physical processes are responsible for the transformation of galaxies from late-type to early-type. We will also search for intra-cluster dust which is expected to be produced via stripping of material from infalling galaxies.
Lead Scientist: Chris Simpson
Allocated time: 27.2 hours
The South Pole Telescope has conducted a large survey of the southern sky at millimeter wavelengths and discovered a population of high-redshift strongly-lensed dusty star forming galaxies. Both the lensing and the long wavelength selection biases these sources to the highest redshift and their apparent luminosity makes them the most best possible candidates for SPIRE FTS spectroscopy. By combining the unique capabilities of SPT as a survey machine and Herschel as a followup spectroscopy machine, we propose to obtain spectra for five of the brightest lensed sources in the sky. These observations will open a new astrophysical window into the study of young star forming galaxies. The ratios of far-IR lines will provide ground-breaking physical information about this earliest stage of galaxy evolution, including the best measures of how star formation is proceeding, dust emission and absorption properties, the detailed physics of the ISM, and also the quantitative contribution of the emission that comes from black hole accretion in an obscured AGN for these high redshift sources.
Lead Scientist: Daniel Marrone
Allocated time: 4.1 hours
One of the most astounding recent discoveries is that 'normal' high-z star-forming galaxies are very gas-rich, and often dominated by a massive, cold molecular interstellar medium (ISM) component. The extended morphology, low gas excitation and low star formation efficiency in these galaxies suggest that they maintain widespread, long-lasting star formation. Thus, the overall conditions for star formation are consistent with nearby spiral galaxies, although scaled up by 1-2 orders of magnitude in gas mass and star formation rate. Building upon our comprehensive study of the molecular ISM in these galaxies, we here aim to explore a new regime of star formation diagnostics in the brightest galaxy in our sample with Herschel, exploiting the unprecedented spectral line sensitivity in the widely unexplored far-infared wavelength regime that is inaccessible from the ground. Using PACS and SPIRE, we aim to detect, for the first time, the seven brightest neutral and low ionization state fine structure ISM cooling lines of C, N, and O in a 'normal' high-z galaxy. These lines will provide a critical piece of evidence for the scenario that the ISM properties in these galaxies are indeed comparable to nearby spirals (rather than extreme starbursts) by constraining the UV radiation field, densities, temperatures, and composition (atoms/ions/molecules) of the gaseous component in our target. Such Herschel data are the last missing piece in a full characterization of the ISM in 'normal' star forming galaxies during the peak epoch of galaxy formation. Together with our extensive ground-based dataset, this will provide a unique template for studies of such galaxies at z>3 with ALMA (where a few of the targeted lines become accessible from the ground).
Lead Scientist: Dominik Riechers
Allocated time: 24 hours
For deep imaging longward of 100 um, confusion noise sets the fundamental sensitivity limits achievable with Herschel, and these limits cannot be improved by integrating longer. To penetrate through this confusion limit and detect faint high-redshift galaxies, gravitational lensing by massive galaxy clusters offers a very powerful and yet cheap solution. For this reason, we are currently conducting a PACS/SPIRE imaging survey of ~40 massive lensing clusters as one of the Herschel Key Programs, "The Herschel Lensing Survey" (PI: Egami, 292.3 hrs). Although this program is producing many exciting results as reported in our 5 Herschel special-issue papers, one thing is becoming clear: it is extremely difficult to find lensed galaxies that are bright enough (> 200 mJy in SPIRE bands) to perform spectroscopy with PACS/SPIRE. This disappointment, however, was quickly overcome by the serendipitous discovery of an exceptionally bright (~500 mJy@350 um) z=2.3 galaxy lensed by a massive cluster at z=0.325. This discovery suggests that if we survey a large enough cluster sample, we will find similarly bright lensed sources that make all kinds of exciting follow-up observations possible. Here, we propose to conduct such a survey by taking advantage of the Millennium Cluster Sample constructed from the ROSAT All-Sky Survey with many years of extensive follow-ups. More specifically, we will conduct a SPIRE snapshot survey of 279 X-ray-selected clusters. SPIRE's great sensitivity and observing efficiency means that we can complete this program in only 27 hours while achieving a nearly confusion-limited sensitivity of 10 mJy (1 sigma). Such a depth will allow all kinds of secondary science projects as well. Although SPIRE wide-area surveys like H-ATLAS will also discover many bright lensed galaxies, these sources are mostly lensed by galaxies and not clusters, which makes our approach an economic alternative to investigate a different type of lensed systems.
Lead Scientist: Eiichi Egami
Allocated time: 27 hours
We propose to use PACS spectroscopy to observe the [OI] 63 um, [OIII] 88 and 52 um, and [OIV] 26 um fine-stucture lines, and PACS/SPIRE photometry to measure the far-IR continuum from 12 IR-bright galaxies in the z = 1 to 2 redshift range. These are galaxies from which we have detected emission in the 158 um [CII] line using our grating spectrometer, ZEUS, on the CSO. We have found that the most luminous starburst-dominated systems in this epoch are characterized by kpc-scale moderate intensity star formation, while the AGN-dominated systems host similarly extended, but much more intense starbursts. The proposed oxygen survey addresses two key questions stimulated by our [CII] results: (1) To what extent are luminous star-forming galaxies at z = 1 to 2 simply scaled-up versions of local starbursts? (2) Why are the starbursts in AGN-dominated systems so much more intense? The oxygen sequence combined with our [CII] detections will have powerful diagnostic capabilities, yielding the strength and hardness of the ambient UV radiation fields, and the density, pressure, and mass of the ionized and neutral atomic components. This data will allow us to characterize the size and age of the starburst, and the importance of the central engine. The ultimate goal is to understand what drives the apparently galaxy-wide starbursts in both star-formation-dominated and AGN-dominated systems, and help identify the connection between starbursts and AGN in the early Universe. This survey is important and unique. We cover the redshift interval from 1 to 2 near the peak of the star formation per unit co-moving volume in the Universe, and it is within this redshift interval that the ZEUS and PACS sensitivities are well matched to enable the detection of the [CII] line together with the oxygen sequence in a wide variety of systems.
Lead Scientist: Gordon Stacey
Allocated time: 45.7 hours
We propose to take advantage of the unique capabilities of both SPIRE and SPT to measure for the first time the ``kinetic SZ contribution'' to the CMB power spectrum. By doing so we will be able to detect, or severely constrain, a signal arising from the scattering of CMB photons off bubbles of ionized IGM during the epoch of reionization, thus providing a first glimpse of the universe as it emerged from the dark ages. To make this measurement we will map the 100 sq. deg. SPT Deep Field with SPIRE and conduct a joint CMB-style analysis of the SPIRE and SPT maps. The high-precision measurements of the CIB fluctuations provided by SPIRE are essential to isolate of the reionization signal. By adding SPIRE observations to the already-reduced SPT data, we will improve the existing constraints on this signal by an order of magnitude. Comparable constraints on the epoch of reionization are unlikely to come from any other combination of facilities prior to the next generation of 21 cm surveys. The combination of the SPT and proposed SPIRE maps will also enable numerous auxiliary studies.
Lead Scientist: John Carlstrom
Allocated time: 79 hours
We propose to obtain deep, spatially--resolved Herschel PACS and SPIRE photometry and PACs and HIFI spectroscopy of the brightest (in the rest-UV) lensed galaxy yet discovered, RCS0327 at z=1.7038. The goal is to characterize the dust--reprocessed spectral energy distribution (SED) of a typical star--forming galaxy at the epoch when half the Universe's stars formed. Because RCS0327 extends across 38 arcsec, Herschel will spatially resolve it, and thus will measure spectral energy distributions in multiple spatially--distinct regions. The resulting SED will serve as one of very few templates of low--extinction star forming galaxies beyond the local universe. We will measure the far-infrared luminosity and thus infer a star formation rate, which we will compare to rates measured from the optical/nIR. Finally, we will measure the luminosities of the [O I] 63 and [C II] 158 micron lines, which with the far-IR luminosity constrain the densities, pressures, and radiation fields of the photo-dissociation regions. Such observations are impossible for Herschel in the distant universe without lensing amplification.
Lead Scientist: Jane Rigby
Allocated time: 19.2 hours
The South Pole Telescope has surveyed 1000 square degrees at millimeter wavelengths down to milli-Jansky levels with the aim of constraining cosmological parameters. One of the most interesting and unanticipated results of this survey was the discovery of a population of high redshift strongly lensed sub-millimeter galaxies (SMGs). The magnification of these objects and the long-wavelength selection makes these source the best window we have to directly investigate massive galaxy formation in the early universe. Here we propose to observe a flux-limited sample of 65 of these sources with PACS and SPIRE for a total of 25.6 hours. These observations will span the peak of the SEDs at all redshifts, determine the redshift distribution and temperatures for these sources, and enable detailed study of molecular and fine structure lines of high-redshift galaxies. These observations are the best method for constraining the properties of the highest redshift SMGs, and we expect to find a minimum of 3 sources at z>5. As these sources are in the southern hemisphere they are ideal targets for ALMA early science observations and will provide an invaluable sample of sources for the community.
Lead Scientist: Joaquin Vieira
Allocated time: 25.6 hours
Gamma-Ray Bursts (GRBs) are so luminous that they can shine through highly obscured galaxies, nearby and in the remote universe. GRBs enable identification of galaxies independently of their luminosity, thus singling out a population that is a potentially powerful probe of galaxy evolution. Only a minority of the host galaxies of GRBs (GRBHs) have been so far detected at sub-millimeter (submm) or mid-infrared (mid-IR) wavelengths; however, in this minority the inferred star-formation rates (SFRs) can be as high as ~500 Msun/year, implying that they are similar to submm galaxies. On the other hand, the frequent non-detections argue against a population dominated by massive and strongly starbursting galaxies. One way to resolve this dilemma would be warm dust. At redshifts 2-4, warm dust (40-50K) would be difficult to detect in the submm bands because its peak would be too blue, and also in the mid-IR, because its peak emission would be far too red. We propose to break this possible dust-temperature redshift "conspiracy" with Herschel PACS+SPIRE photometry of 14 GRBHs with redshifts reaching 4.4. The sample was selected on the basis of prior Spitzer IRAC (or MIPS) detections. We already have in hand a large amount of ancillary multiwavelength data with which we can determine stellar ages and masses. We will construct spectral energy distributions from the UV to the far-IR and use them to derive bolometric luminosities and SFRs, and constrain dust mass, dust temperature, and grain properties. We will compare the dust properties with the stellar component of the galaxies, and analyze the GRBHs in the context of other high-z galaxy populations. Such a program is now possible thanks to the unique ability of Herschel to study dust emission in galaxies over a wide range of redshifts. Ultimately our proposed study of GRBHs will open a new window on the study of galaxy formation and evolution.
Lead Scientist: Leslie Hunt
Allocated time: 28.1 hours
Ultra luminous dusty galaxies radiating most of their energy in the far IR are now known from Spitzer IR and submillimeter observations to dominate the integrated luminosity at redshift 2 to 3. The behavior of this population at higher redshifts remains poorly constrained. This proposal is based on the use of the Planck all sky survey at millimeter and submillimeter wavelengths to find new and rare high-z candidate sources. The limited angular resolution requires a specific data processing to extract good candidates. The Cosmic Infrared Background (CIB) is observed with high signal to noise by Planck after a specific component separation. An algorithm detecting cold spots on the CIB (thus potentially high z dominated) compatible with point sources has been developed. These high z blobs have been shown to be a mixture of different type of objects. Among these, new high z ULIRGS at the high end of the luminosity function or lensed, or high z large scale structures are very interesting for galaxy evolution. We performed comparison of the Planck data with new unidentified sources found by SPT near the upper end of their luminosity function and we detected a few of them. Furthermore, the stacking in Planck of 34 of these SPT sources is easily detected in Planck and gives a typical SED in the Planck bands for these sources. We thus selected sources with this type of SED in the Planck data and produced a list of 10 candidates proposed in this program for observations with SPIRE and PACS. We propose an observation allowing to study the nature of these 10 cold blobs in three cases covering well the possible contributors to this Planck detected high z blobs (single source, cluster of 10 to 20 sources, structure of the cold CIB spot if a small number of sources has not been found). This should be a very interesting contribution to the study of this new emerging population. Furthermore this program should allow us to use best the Planck all sky survey later to find more candidates.
Lead Scientist: Ludovic Montier
Allocated time: 11.6 hours
We have recently discovered a population of 'super-starbursts' at z~1-3-1.5. These rare galaxies are selected from the zWiggles spectroscopic survey, and rest-frame UV and H-alpha spectroscopy suggests star-formation rates 100-500Mo/yr. These apparently high-luminosity, but low stellar mass (log(Mstar)~10Mo), gas rich (f_gas~60%) galaxies forming extremely quickly in an extended starburst are suggestive of late time proto-galaxies, but uniquely, are selected from their nebular emission lines. We have obtained three dimensional spectroscopy of 13 galaxies and mapped the two dimensional dynamics on ~kpc scales. The galaxies show extended star-formation on 4--16kpc scales, with dynamics which may resemble rotating systems and clumpy and intense star-formation which may indicate bulge formation. However, the impact of dust obscuration is unknown, and if these galaxies are confirmed as high luminosity ULIRGs, it would argue that these are instead mergers with structures dust, and instead comprise the low-redshift tail of the 'archetypal' high-z ULIRGs and SMGs seen at z~2.3. We propose short Herschel SPIRE observations of this sample of 13 galaxies. We conservatively predict 250um fluxes >12mJy, which should yield detections viable in just ~7mins each. Our total request 6.7 hours.
Lead Scientist: Mark Swinbank
Allocated time: 6.7 hours
One of the most fundamental correlations between the properties of galaxies in the local Universe is the so-called morphology-density relation. In the local Universe late type star forming galaxies favor low density regimes and giant ellipticals reside in the cluster cores. Much of the debate centers on whether the relation arises early on during the formation of the object, or whether it is caused by environment-driven evolution. To shed ligth on this issue, we propose to map with PACS at 100 and 160 um the field of 8 clusters in the ``cluster desert'' at 1.4 < z < 1.8, at the epoch when clusters are accreting galaxies and galaxies are still undergoing their own formation process. Our goal is to observe each system down to log(LIR)=11.5 to observe almost the entire LIRGs and the complete ULIRGs population and to sample the bulk of the star formation. The 8 systems are all X-ray detected, spectroscopically confirmed and with large amount of multi-wavelength ancillary data. The X-ray detection ensures that these are well established, bound structures, which represent the missing link between the protoclusters at z > 2 and the well formed clusters in the local Universe. Our sample spans almost a decade in X-ray luminosity and dynamical mass, comprising relatively young systems and already old and relaxed clusters. This hetereogenity allows us to link the level of star formation activity to the global properties of the systems to shed light on which environmental process, if any, can affect the galaxy star formation activity. All systems are covered by medium-deep and deep XMM and Chandra data, crucial to reveal X-ray faint AGNs, and to study the connection between AGN feedback and star formation activity. The availability of accurate stellar mass estimates allows to relate the SF activity to the environment in different mass bins, thus disentangling the mass- from the environment-driven galaxy evolution.
Lead Scientist: Paola Popesso
Allocated time: 97.4 hours
We have recently discovered the most distant X-ray luminous galaxy cluster known to date, a z=2.07 strong overdensity of red passively evolving ellipticals with extended X-ray emission seen by XMM-Newton. Several cluster members are detected by MIPS at 24 micron with fluxes above 100 microJy, implying high luminosities in the mid-IR rest frame. If due to star formation activity this would correspond to ULIRG-like luminosities, and would imply a very high degree of forming activity in the cluster core. However, the MIPS detected galaxies have elliptical like morphologies and SEDs, suggesting in turn that the mid-IR emission is due to a huge amount of heavily obscured AGN activity. We propose deep imaging with PACS and SPIRE in the cluster that will clarify the AGN or SF nature of the activity in the cluster. Our results will have important implications on the understanding of the early phases of cluster galaxy assembly. This project will push the study of galaxy activity in established clusters to the highest possible redshifts.
Lead Scientist: Raphael Gobat
Allocated time: 17.7 hours
The progenitors of local galaxy clusters ("proto-clusters") are powerful laboratories for tracing the emergence of large scale structure and studying the evolution of galaxies in dense environments. We propose to use SPIRE's excellent sensitivity and survey speed to obtain, for the first time, a large sample of dust-obscured, star forming, proto-cluster galaxies in an area encompassing the entire proto-cluster and its environment. The 8 proto-clusters in the sample cover the key redshift range 2 < z < 4 and have a wealth of existing, multi-wavelength data and a large number of spectroscopically confirmed proto-cluster galaxies. The masses of the proto-clusters are typically a few times 10^14 - 10^15 solar masses and the cores are up to 40 times denser than the field. Matching the SPIRE sources with upcoming LOFAR and EVLA radio observations, we will constrain the photometric redshifts to better than 0.3, resulting in a complete sample of dusty proto-cluster galaxies with very low (<5%) contamination. The proposed SPIRE observations will be compared to our extensive simulations of forming proto-clusters, allowing us to: (i) unveil and characterize the (dust-obscured) star-forming galaxies in the proto-clusters and constrain their star formations rates and dust temperature; (ii) relate these properties to their optical morphologies, stellar masses and location in the proto-cluster and investigate the differences between proto-cluster galaxies and field galaxies; (iii) ascertain whether red proto-cluster galaxies are passive galaxies or dusty starbursts; (iv) determine the structure and size of the proto-clusters, in particular, distinguish whether galaxies are distributed homogeneously or in filaments; (v) trace the evolution and contraction of large-scale structures from z=4 to z=2. The proto-cluster targets are ideally located for follow-up spectroscopy and high-resolution imaging with submm observatories such as APEX and ALMA.
Lead Scientist: Hubb Röttgering
Allocated time: 16.7 hours
Characterising the ISM of bright, lensed star-forming galaxies across cosmic time with the SPIRE FTS
We have shown that Herschel is capable of exploring high-redshift galaxies spectroscopically, provided those galaxies are sufficiently bright. Here, we propose to exploit the wide wavelength coverage of the SPIRE FTS to study the powerful diagnostic rest-frame FIR cooling lines from a unique and complete sample of 25 bright, gravitationally-lensed - but intrinsically typical - submm galaxies (SMGs). We can thus perform the first detailed analysis of their ISM, tracing their density structure and searching for variations in line strengths compared to local counterparts. Our targets span 1 < z < 3.1 (where [C II] is not accessible to ALMA) and a good range of L(FIR) (12 < log L(FIR) < 13.5), and are selected from panoramic Herschel imaging surveys that are uniquely capable of providing a large, reliable sample at S(350um) > 200mJy, with excellent ancillary data.We will detect or place sensitive limits on the key atomic cooling lines, e.g. [C II], [O I], [O III], and combine these with ground-based observations of 12CO, 13CO, C I and dense-gas tracers to model their ISM and thence understand their energetics and evolution. Using these data we will: 1) map the evolution of the gas content as a function of redshift, via the sensitivity of [C II]/L(FIR) to M(H2); 2) search for changes in the properties of the star-forming gas as a function of redshift and L(FIR); 3) coadd the spectra in the rest frame to delve up to 5x deeper still, to search for faint lines, e.g. H2O and [O I]145.5, allowing a complete characterisation of the average emission; 4) conclusively address the issue of the contribution of AGN to the immense luminosities of submm galaxies. Goals 1-3 drive the requirement for a sample of 25 SMGs. All our goals require Herschel and cannot be addressed by other facilities. We stress that the scientific legacy of ISO and Spitzer has in large part been based on the wealth of data in their spectroscopic archives and the same is likely to be true for Herschel.
Lead Scientist: Rob Ivison
Allocated time: 94.1 hours
We have discovered a z=6.1 Submillimetre Galaxy from a detailed survey of 0.5 sq deg in GOODS-N, FLS, and LockmanEast. HDF259 was originally detected by SCUBA and the VLA, but recently constrained through Herschel-SPIRE detections. The redshift is confirmed through a Keck spectroscopic redshift, an optical-near/mid-IR photo-z (as an I-band dropout with a rising stellar bump at 1.6um), and through template fitting with a most likely T_dust in the SPIRE through 1.2mm wavelengths. Even if the optical data incorrect redshift, an extreme range of T_dust secures the redshift as lying from z=4-8. This SMG represents the first opportunity yet to study the rest-frame 7.7um region PAH features in a z>6 star forming galaxy, using the PACS spectrometer (where the 7.7um strong PAH feature comes into the PACS 51-70um and 70-105um bands only at z>5.9). The strength of the PAH, estimated both from extrapolated flux measurements from Spitzer-MIPS, and from the z~2 L_IR-L_PAH relation (Pope et al. 2008) ensures that a typical PAH in this SMG will be well detected in 4.8hrs total programme duration.
Lead Scientist: Scott Chapman
Allocated time: 4.8 hours
THE HERSCHEL-AKARI NEP DEEP SURVEY: the cosmological history of stellar mass assembly and black hole accretion
We propose a far-IR and submm mapping survey of the premier AKARI deep field in the North Ecliptic Pole, in PACS/SPIRE parallel mode. This is the only major deep infrared field not yet covered by Herschel guaranteed or open time key projects. The outstanding and unparalleled continuous mid-IR photometric coverage from AKARI, far better than equivalent Spitzer surveys, enables a wide range of galaxy evolution diagnostics unachievable in any other survey field (including Herschel HerMES/PEP fields), by spanning the wavelengths of redshifted PAH and silicate features and the peak energy output of AGN dust tori. The investment by AKARI in the NEP represents ~10 percent of the entire pointed observations available throughout the lifetime of AKARI. Our proposal remedies the remarkable omission from Herschel's legacy surveys of the premier extragalactic deep field from another IR space telescope. We will simultaneously identify and find photometric redshifts for the Herschel point source population, make stacking analysis detections of the galaxies which dominate the submm extragalactic background light as a function of redshift, determine the bolometric power outputs of the galaxies that dominate the submm background, compare the UV/optical/mid-IR continuum/PAH/far-IR/submm/radio star formation rate estimator in the most comprehensive IR survey data set to date, and track the coupled stellar mass assembly and black hole accretion throughout most of the history of the Universe.
Lead Scientist: Stephen Serjeant
Allocated time: 73.5 hours
We propose to detect dust associated with ram-pressure stripping through deep Herschel PACS/SPIRE imaging of a carefully chosen set of cluster galaxies that show strong signs of on-going stripping and intracluster star formation. Several lines of evidence, such as the existence of cold molecular gas and intracluster star formation in ram-pressure stripped tails, strongly point towards the existence of dust in these tails. Herschel is the only telescope that has the sensitivity to detect the emission from dust blown out into the intracluster medium (ICM). With our proposed observations we aim to: 1. quantify the temperature, mass, and lifetime of dust blown out into the ICM; 2. understand the role dust plays in the existence of molecular hydrogen in the ICM and intracluster star formation. Our program will carry out deep Herschel observations of five galaxies in high pressure environments with highly extended (~20-80 kpc) multi-phase gaseous tails. The Herschel observations will expand our already large multi-wavelength dataset and finally provide complete inventory of the gas and dust associated with ram-pressure stripping. This will provide a more complete picture of the impact of ram-pressure on galaxy evolution.
Lead Scientist: Suresh Sivanandam
Allocated time: 10.4 hours
We propose to obtain deep PACS + SPIRE far-IR photometry and 2D PACS [C II] 158 um spectroscopy of 7 cooling-flow clusters with extended Halpha filaments to constrain the properties of the dust and cooling gas in these systems. Our targets are part of a large sample of clusters that were imaged at Halpha using the Maryland Magellan Tunable Filter (MMTF) as part of a comprehensive multiwavelength survey. The superb sensitivity and resolution of the MMTF data have uncovered, often for the very first time, spectacular filaments of warm ionized gas extending as far as 50 kpc from the cluster core. The origin and heating source of these filaments remains a mystery. Our MMTF images have served as a guide to extract on-filament X-ray and optical spectra for a large sample of clusters, leading to the discovery that the X-ray ICM is cooling at a highly accelerated rate in the vicinity of these filaments. This direct link between the warm and hot phases may be the first direct evidence for the purported cooling flow. Given the high FIR fluxes detected in cluster cores, it is possible that dust grain cooling plays an important role in the cooling flow process. However, it remains unclear whether the observed dust is associated with the warm filaments or limited to the center of the brightest cluster galaxy (BCG). Current key programs cannot address this question given their lack of information on the Halpha filaments. Our proposed Herschel observations of the 7 cooling-flows clusters from our sample with the most extended Halpha filaments will directly address this question and help us determine: a) the role of dust cooling in the cooling-flow process, b) whether the observed dust is associated with the BCG or the warm filaments, and c) whether gas is cooling below 10^4 K, the temperature probed by Halpha. Providing answers to these questions will improve our understanding of the cooling processes in galaxy clusters and constrain the role of heating processes, such as AGN feedback, in preventing such cooling.
Lead Scientist: Sylvain Veilleux
Allocated time: 7 hours
A deep PACS survey of AKARI-Deep field south: Revealing the connection between AGN and star formation
We propose a deep PACS imaging survey of a prestigious far-IR survey field, AKARI-Deep field south, which has the lowest cirrus background in the sky and has been observed with most of the major IR and submm telescopes, such as AKARI, Spitzer/MIPS, BLAST and Herschel/HerMES, covering 7-12 deg^2. We also conducted one of the widest and deepest millimetre survey using ASTE/AzTEC within this field, covering 0.25 deg^2. Although there are many (sub)mm survey fields in different parts of the sky, ADF-S has a unique data set from AKARI/IRC at 2.4, 3.2, 4.1, 7, 11, 15 micron, i.e. filling the wavelength gap between Spitzer/IRAC 8 micron and MIPS 24 micron. We utilize this comprehensive mid-IR coverage to identify obscured AGNs and derive the bolometric AGN luminosity, based on the type-independent X-ray-to-mid-IR luminosity relation. PACS photometry is necessary to derive accurate star formation rate (SFR) in starburst-AGN composite system. We investigate the relative importance of AGN in SMGs and other mid-IR selected ULIRGs, as a function of SFR, stellar mass, and redshift. Ultimately, we will determine the role of AGN in galaxy formation and the regulation mechanism for co-evolution of stellar mass assembly and central black hole. Also, deep PACS images allow us to identify millimeter-selected SMGs at very high redshifts, which will be prime targets of ALMA.
Lead Scientist: Toshinobu Takagi
Allocated time: 34.5 hours
We propose deep five-band imaging with SPIRE and PACS of 10 of the most massive galaxy clusters in a 455 square degree southern strip surveyed by the Atacama Cosmology Telescope (ACT). Our targets lie at 0.3 < z < 1.1 and were identified by their 2mm Sunyaev-Zel'dovich Effect (SZE) decrements, which provide a redshift-independent mass selection, and confirmed with optical imaging. Herschel observations, building on X-ray, optical, near-IR, submillimeter, and radio data, will allow us to study how star formation within individual galaxy members and integrated across clusters is influenced by the process of cluster assembly in the most massive systems out to z ~ 1. We will also extract our targets' SZE decrement/increment spectra and mass profiles, providing useful inputs to the cross-calibration and interpretation of large SZE surveys. Finally, our observations will exploit the clusters' gravitational lensing for the detection of dusty background galaxies, down to flux levels that would otherwise be below the confusion limit of blank-field imaging. By combining PACS and SPIRE data with our ancillary observations, we will be able to determine photometric redshifts for these background galaxies sufficiently well to allow followup observations with ALMA, for which our fields' southern declinations are ideal, in order to understand the detailed physical properties of dusty star-forming galaxies at high redshift.
Lead Scientist: Andrew Baker
Allocated time: 30 hours
Large-scale filaments are home to about 1/3 of all galaxies in the universe. Their characteristics make them ideal environments for galaxy-galaxy mergers and interactions, leading to bursts of star-formation, visible in the infra-red (IR). So far, only a few studies of filament galaxies exist, and even fewer including mid- or far-IR observations. We propose to partially fill this gap in our knowledge of galaxy evolution by observing a 14 Mpc long filament of galaxies connecting two clusters at redshift 0.23, with PACS and SPIRE for a total time of 18.1 hours. Complemented with already available extensive optical spectroscopic (1413 galaxies) and multiwavelength photometric data (including mid-IR data from Spitzer for one cluster and part of the filament), the new Herschel data will allow us to determine the galaxy (specific) star-formation rates as a function of their location in the filament with respect to the two clusters. This will help constraining which physical processes are responsible for the excess of star-forming galaxies in the filament relative to both denser and less dense galaxy environments, discovered in our previous studies of this region (Fadda et al. 2008, Edwards et al. 2010a,b, Biviano et al. 2011).
Lead Scientist: Andrea Biviano
Allocated time: 18.1 hours
The star formation activity in a present-day galaxy is strongly correlated with the environment in which the galaxy lives. Passive, spheroidal systems are preferentially found in the core of clusters, whereas star forming, late-type galaxies inhabit low-density environments, from the field to the outskirts of clusters. Therefore, galaxy clusters are the best places where to probe galaxy transformation. Different mechanisms can contribute in driving galaxy transformations by depleting the galaxy of its cold gas reservoir and decreasing the star formation activity. Ram pressure stripping, harassment and galaxy-galaxy collisions are likely to play a role but it is still unclear which of these are the dominant mechanisms driving galaxy evolution inside clusters. In the continuos gold rush toward the highest redshift galaxies the local environment has long been neglected. In this proposal we aim to study the star formation activity and the galaxy dust role in nearby galaxy clusters (0.04<z<0.07) as a function of environment by probing the broadest possible range of environments from the core of rich clusters to the outskirts, where the main processes modifying galaxy properties occur.
Lead Scientist: Antonio Cava
Allocated time: 20.6 hours
The ISM content and the SF History of Two Clusters with Very Distinct Environments at z=0.2: Abell 963 vs. Abell 2192
We propose to image 1 sq. degree regions centered on Abell 963 and Abell 2192 in PACS/SPIRE parallel mode. These two galaxy clusters have very distinct environments yet both are located at z~0.2, where the Butcher-Oemler effect (the fraction of blue galaxies near the cluster center increases with redshift) begins to show. To identify physical mechanisms driving galaxy evolution in clusters at this redshift, our team initiated a multi-wavelength study of Abell 963, a rich cluster with a high fraction of blue galaxies around z~0.2, and Abell 2192, a less massive cluster with a low dispersion at a similar redshift. With the goal of relating the star formation activity with the ISM content, we have obtained deep WSRT HI imaging data, which is unique to date at this redshift. Besides HI data, we have collected radio continuum, mid infrared, optical, and UV data to diagnose the ISM removal processes and to study detailed star formation histories. In addition, we will start a CO survey of the two clusters in the near future to measure the total cool gas mass. Our multi-wavelength survey area is large (> 10 Mpc in diameter on the sky) enough to include low-density environments where galaxies appear to undergo significant evolution. The Herschel data will allow us to map out the entire IR SED of various galaxy populations and also to study dust properties, which is essential for this study. We request 40.3 hrs of Herschel time to obtain 9 PACS/SPIRE scans over 1 sq. degree field centered on each cluster (18 scans in total) to achieve the enough sensitivity to detect L* galaxies in each cluster.
Lead Scientist: Aeree Chung
Allocated time: 40.3 hours
In massive galaxies the AGN at the core can have a profound effect on its host galaxy from their formation to the present day. This effect is particularly important in the cores of clusters of galaxies where the AGN is believed to be strongly suppressing the cooling of the hot intracluster gas that surrounds the brightest cluster galaxy (BCG). We propose to obtain PACS photometry and spectroscopy of four BCGs that have strong AGN characteristics ([OIII] line, MIR continuum and/or flat spectrum radio continuum). These four systems are the most extreme BCGs selected from a sample of over one thousand X-ray selected clusters and hence can be used to constrain the energetics and duty cycle of AGN in a statistically meaningful sample of clusters. The Herschel data will reveal important diagnostics of the individual AGN that can be applied to weak AGN in the larger sample.
Lead Scientist: Alastair Edge
Allocated time: 8.4 hours
Recent observations suggest a reversal in the star formation rate density relation at z>1 such that the average star formation rate in galaxies increases with increasing local galaxy density. Two high redshift clusters have shown an increased fraction of actively star forming galaxies towards the center of the cluster, albeit with small number statistics, but the epoch at which this transition occurs is poorly constrained. We propose a statistical study of the dust−obscured star formation activity in a mass-limited sample of 11 spectroscopically-confirmed clusters from z=1.1-1.8 with PACS imaging at 100/160 microns. With 54.7 hours of observing time, we will detect ~150 cluster galaxies down to 100 solar masses per year and many more field galaxies. Our sample spans the fundamental redshift range during which massive clusters show signs of transitioning from a stage of active formation to passive evolution. We will determine the role of the cluster environment on the evolution of infrared luminous galaxies as a function of redshift. These Herschel observations will allow us to map out the star formation activity in galaxy clusters and constrain their mass assembly epoch.
Lead Scientist: Alexandra Pope
Allocated time: 54.7 hours
Massive clusters of galaxies have been found to date from as early as 3-4 billion years after the Big Bang. Cosmological simulations using the current cold dark matter model predict that these systems should descend from 'proto-clusters' - early overdensities of massive galaxies that merge hierarchically to form a cluster. These protocluster regions themselves are built up hierarchically and so are expected to contain extremely massive galaxies, progenitors of the quiescent behemoths observed in cores of the present day massive galaxy clusters. Observational evidence for this picture, however, is sparse because high-redshift proto-clusters are rare and difficult to observe. Here we propose to probe with Herschel SPIRE the very beginning of the cluster and massive galaxies formation process by observing 5 proto-clusters at 3<z<4. The aim of the project is to observe the entire Ultraluminous IR galaxy (ULIRG) population, dominating the bulk of the star formation at such high redshift, to compare the properties of the proto-cluster galaxies with those of field galaxies at similar redshift. Determining whether cluster galaxies differ from field galaxies when the proto-cluster was still forming, tells us whether any of the difference observed today is driven by nature as apposed to nurture.
Lead Scientist: Bruno Altieri
Allocated time: 5 hours
We propose to measure the dust properties and far-iR star formation rates (SFR) of high redshift type Ia supernova (SN Ia) host galaxies to improve their use as cosmic probes. In fitting SN Ia light curves, we must fit both the intrinsic color variation of the SN and dust together, limiting their statistical precision. Using light curve fitting, SN Ia have been observed to have a wide range of dust values and laws, some that are very different from the Milky Way. Additionally, after correction, SN Ia light curves show a dependency on their ultraviolet (UV) specific SFR's (sSFR), however the UV is sensitive to dust and thus our UV SFRs might be underestimated. We propose to take PACS and SPIRE observations of 74 high redshift host galaxies of SN Ia discovered by the ESSENCE project. We will measure the dust mass and temperature, using this information to re-analyze SN Ia light curves and study their intrinsic properties. We will also measure the far-IR SFRs to look for correlations and dependancies of SN Ia's on their host galaxies. All of this information will be used to improve and refine our measurements of Dark Energy.
Lead Scientist: Brad Tucker
Allocated time: 57.5 hours
Using data from the NASA Wide-field Infrared Survey Explorer (WISE) mission coupled with deep optical spectroscopy, we have discovered a new population of dusty z~2 galaxies surrounded by large spatially extended Lyman-alpha emission (40-100kpc). These galaxies have redder mid-IR colors than any other high-z dusty populations, inferred IR luminosities of L_FIR>10^13, are unlensed, and are experiencing intense AGN/supernova feedback. These unique properties, and rarity on the sky, make them strong candidates for being one of the ``missing links'' in the evolution of massive ellipticals. They have opened up a new regime where spatially extended Ly-alpha and large amounts of dust are likely linked at the key transition from a dusty starburst to a QSO.
We request 5.6 hours to obtain Herschel-PACS and SPIRE imaging of *all* 18 spectroscopically confirmed WISE Ly-alpha blobs. Herschel is the only facility that fully probes the peak of the bolometric emission at this redshift. These observations are required in order to 1) derive precise FIR luminosities 2) place robust constraints on the starburst and AGN components 3) study how feedback effects the shape of far-IR seds at high-z 4) uncover what is driving the winds responsible for powering the Ly-alpha clouds around these dusty galaxies and 5) place this new class of extreme object in context with the other well studied z~2 dusty galaxies.
Lead Scientist: Carrie Bridge
Allocated time: 5.6 hours
We propose to continue our study of the high-z galaxy SMMJ02399-0136 at z=2.8 by observing with Herschel several bright far-IR fine-structure lines from O, N, and C, as well as its rest-frame mid- and far-IR continuum. This source is an excellent target of study because it has been extensively observed in other wavelengths, we have previously detected it in the [NII] 122 and [OIII] 88 micron lines, using ZEUS on the CSO, and it resides in the epoch of peak star formation in the Universe. Furthermore, SMMJ02399 is a multi-component system with AGN and starburst components at different relative velocities. Thus it presents the unique opportunity of observing an AGN, a starburst, and their interaction simultaneously from a source at high-z. The sensitivity, resolution, and broad spectral coverage of Herschels spectrometers, makes Herschel the ideal observatory from which we can make these observations. For several lines, it is the only observatory capable. Our proposed Herschel observations will allow us to determine the AGN and starburst contribution to the lines, characterize the starburst and the narrow-line region of the AGN, and explore the relationships between star formation and AGN in galaxies in the early universe.
Lead Scientist: Carl Ferkinhoff
Allocated time: 10.7 hours
We are conducting a survey of the [CII] 158um line from galaxies at redshifts 1-2 using our grating spectrometer, ZEUS on the CSO. Our first 13 galaxy survey showed that luminous star forming galaxies in this epoch have moderate intensity kpc-scale star formation – likely an extension of the Schmidt-Kennicutt law to very high gas mass fractions. Our AGN dominated systems have similarly large scale, but significantly more intense star formation suggesting punctuated, collision-induced star formation. We were awarded OT1 PACS spectroscopy and PACS/SPIRE photometry of these sources to observe the oxygen [OI], [OIII], and [OIV] fine-structure lines and far-IR continuum to characterize the star formation and AGN activity in these sources. Only two of our sources have been observed to date, but with good astrophysical success. Since the OT1 submission, we have detected 11 more z ~1-2 sources in [CII] with ZEUS. Here we propose an OT2 oxygen line/far-IR continuum study for 10 of these new sources. The new source list significantly enhances our OT1 survey in that (1) we nearly double our sample greatly increasing statistical significance of the results (2) the new group includes 7 Spitzer/PAH sources. PAH emission arises from PDRs tracing the photo-electric heating, while the [CII] and [OI] lines trace the cooling. PAHS therefore trace star formation and, since the features are extremely bright, are excellent redshift indicators. Future missions (e.g. JWST and SPICA/SAFARI) will rely on PAH spectroscopy at high z. It is therefore vital to study PAH emission and its relationship to star formation. The proposed work explores this connection at redshifts 1-2, near the peak of star formation per unit co-moving volume over cosmic time. In this interval ZEUS and PACs share a great synergy with well-matched sensitivities enabling detections of [CII] and oxygen in a wide variety of systems.
Lead Scientist: Drew Brisbin
Allocated time: 27.6 hours
We propose to observe with PACS and SPIRE the unique system of Abell 85: a rich cluster with a feeding filament detected in the X-ray. Through extensive optical spectroscopy, we already detected an overdensity of star-forming galaxies along the filament. Infrared observations, in conjuction with newly obtained GALEX data, will allow us to obtain a complete census of the obscured and unobscured star forming activity along the filament and inside the cluster. Since galaxies are infalling onto the cluster along the filament, this corresponds to studying the different stages of evolution of galaxies during the infall. Moreover, due to the vicinity of the cluster (z=0.055), we will obtain images deep enough to detect dwarf galaxies, those most affected by the environment for which we expect the largest variations in specific star formation.
Lead Scientist: Dario Fadda
Allocated time: 21.4 hours
We propose a deep and wide PACS 100 and 160micron survey of the Extended Groth Strip (EGS) region, providing an area/depth combination that is unique to Herschel deep fields and leveraging the excellent existing multiwavelength database for this field from AEGIS, CANDELS, Fidel, GTC, IRAM PdB, and other projects. With unprecedented statistics, our observations will probe `calorimetric' star formation rates based on the rest frame far-infrared SED peak, down to galaxies on the z~1 main sequence. We will characterise scalings between star formation rate, stellar mass, gas mass, dynamical mass, morphology, metallicity of typical z~1 galaxies. EGS is unrivaled for study of the effects of galaxy environment. The deep Herschel data in combination with the unique Chandra coverage for a field of this size will permit to study star formation in AGN hosts in a luminosity and redshift regime where previous results give tantalising evidence for a transition between secularly evolving hosts and more violent short term effects, but where previous Herschel datasets are limited in either statistics or depth. Beyond these two core science questions, the combination of the new Herschel data, with an estimated 3000-4000 sources, and the rich EGS multiwavelength database will permit a broad range of legacy galaxy evolution studies and provide a lasting archival value.
Lead Scientist: Dieter Lutz
Allocated time: 150.7 hours
Imaging surveys have identified and counted a major population of very bright, massive, dusty galaxies at high redshifts. To understand the astrophysics of this population, i.e., how they generate their luminosities, requires Herschel spectroscopy of their strong diagnostic FIR fine-structure emission lines. The very large sky area surveyed by SPT provides a unique sample of such galaxies at z=2.5-6, i.e., viewed when the Universe was only 1-2 Gyrs old. They are especially bright, and therefore suitable for spectroscopy, because gravitational lensing has magnified them by 10-30 times. We propose a 2-pronged program of PACS and SPIRE spectroscopy to measure the full range of ISM ionizations, from OI, to OIII and in some cases OIV, in 17 dusty, young galaxies. The resulting line ratios will provide the first quantitative estimates of the emission from star formation, PDRs, and a possible AGN, independent of absorption. (In some galaxies, our proposed spectroscopy may be sensitive enough to detect OH lines in either absorption or emission).
Lead Scientist: Daniel Marrone
Allocated time: 76.6 hours
We propose to conduct a survey of the host galaxies of dark gamma-ray bursts (GRBs), events whose optical afterglow flux was severely diminshed by dust within their host galaxy (and which historically have been significantly under-represented in host catalogs). Our multi-year campaign of ground- and space-based follow-up has shown that these galaxies are much redder, more luminous, and generally more diverse than ordinary GRB host galaxies, making them promising candidates for long-wavelenength follow-up. Ground-based searches for radio and submillimeter emission have so far been fruitless - yet if GRBs are indeed representative of the sites of high-redshift star-formation, large far-IR luminosities are expected for some GRB hosts. By observing at the dust emission peak, PACS is particularly sensitive to dust reradiation and is relatively unaffected by variations in dust temperature, making it ideal for finding and characterizing this elusive emission. Our PACS observations will measure or tightly constrain the far-IR luminosity and dust temperatures of many dark GRB hosts and thereby calculate the total star-formation rate and obscuration fraction of this sample. These observations, combined with our large ground- and space-based optical/NIR/MIR observing programs, will definitively reveal to what extent the obscuration properties and bolometric luminosities of dark GRB hosts resemble those of ordinary GRB hosts and of star-forming galaxy populations generally, and evaluate in detail the use of GRBs as high-z star-formation tracers. Our sample has been carefully chosen to ensure all targets are heavily dust-obscured GRBs (and not simply underluminous or poorly-observed); to represent the full range of diversity seen among dark GRB host galaxies; to have excellent existing multiwavelength follow-up with other instruments; and to optimize the detectability of the sample to Herschel, even in the pessimistic case that GRB hosts harbor little highly dust-embedded star formation.
Lead Scientist: Daniel Perley
Allocated time: 36.7 hours
In our deep, "blind" wide-band millimeter spectroscopic follow-up campaign on HerMES Herschel/SPIRE sources, we have recently made a spectacular discovery. Based on the secure identification of a suite of atomic fine structure and molecular lines, we have discovered Herschel's "first-born" starburst, a submillimeter galaxy at an unprecedented redshift of z=6.34, when the Universe was only 885 million years old. This source, dubbed FLS3, has a 250um to 20cm spectral energy distribution (SED) comparable to lower redshift starbursts (in the rest frame). However, due to its extreme redshift, the blue wing of the SED below 250um (rest-frame 34um) is only poorly constrained. This prevents investigations of the potential presence of warm, >100K dust associated with a dust-enshrouded, optically faint active galactic nucleus (AGN), for which there may be tentative evidence in the extensive, panchromatic dataset we were able to assemble on this source over the past three months. PACS photometry is perfectly suited to remedy this unfortunate gap in our wavelength coverage, as it covers the rest-frame 8-29um range - ideal to investigate the presence of warm dust associated with an obscured AGN. The proposed, inexpensive study (only 3.9hr of PACS photometry) will offer us a first glimpse into the science that SPICA will enable in the very early Universe at the end of this decade.
Lead Scientist: Dominik Riechers
Allocated time: 3.9 hours
For deep imaging longward of 100 um, confusion noise sets the fundamental sensitivity limits achievable with Herschel, and these limits cannot be improved by integrating longer. To penetrate through this confusion limit and detect faint high-redshift galaxies, gravitational lensing by massive galaxy clusters offers a very powerful and yet cheap solution. For this reason, our team has been conducting a PACS/SPIRE imaging survey of 44 massive lensing clusters as one of the Herschel Key Programs, "The Herschel Lensing Survey" (PI: Egami, 292.3 hrs). Deep PACS/SPIRE imaging data of massive clusters are quite rich with a variety of information, which allows us to study not only the properties of gravitationally lensed high-redshift galaxies but also those of cluster member galaxies and the intracluster medium through the analysis of the Sunyaev-Zel'dovich effect.
In January 2010, a massive HST program targeting powerful lensing clusters was accepted as one of the three multi-cycle treasury (MCT) programs. This program, ``the Cluster Lensing And Supernova survey with Hubble'' (CLASH), has an allocation of 524 orbits, and will obtain deep ACS and WFC3 images of 25 massive galaxy clusters using 16 broad-band filters from near-UV (2250 A) to near-IR (1.6 um). These extensive multi-filter imaging observations will produce high-precision photometric redshifts (sigma/(1+z)<0.02). On average, the program spends 20 orbits per cluster. Considering this enormous investment of HST time, the CLASH program will define the ultimate sample of massive galaxy clusters on which future studies will focus.
Here, we propose to obtain deep PACS and SPIRE images for 10 CLASH clusters that still lack such data (the other 15 clusters already have a good Herschel coverage). To fully exploit the combination of the Herschel and HST data, the HLS and CLASH teams are submitting this proposal jointly with the participation of key scientists from both teams.
Lead Scientist: Eiichi Egami
Allocated time: 48.2 hours
On the extragalactic side, one of the most remarkable results coming out of Herschel is the discovery of extremely bright (>100 mJy in the SPIRE bands) gravitationally lensed galaxies. The great sensitivity and mapping speed of SPIRE have enabled us to find these rare extraordinary objects. What is truly exciting about these bright lensed galaxies is that they enable a variety of detailed multi-wavelength follow-up observations, shedding new light on the physical properties of these high-redshift sources. In this regard, our OT1 program, "SPIRE Snapshot Survey of Massive Galaxy Clusters" turned out to be a great success. After imaging ~50 galaxies out of 279 in the program, we have already found two spectacularly bright lensed galaxies, one of which is at a redshift of 4.69. This type of cluster-lensed sources are not only bright but also spatially stretched over a large scale, so ALMA (or NOEMA in the north) is likely to be able to study them at the level of individual GMCs. Such studies will open up a new frontier in the study of high-redshift galaxies.
Here, we propose to extend this highly efficient and effective survey of gravitationally lensed galaxies to another 353 clusters carefully chosen from the SPT and CODEX cluster samples. These samples contain newly discovered high-redshift (z>0.3) massive (>3-4e14 Msun) clusters, which can be used as powerful gravitational lenses to magnify sources at high redshift. With the OT1 and OT2 surveys together, we expect to find ~20 highly magnified SPIRE sources with exceptional brightnesses (assuming a discovery rate of ~1/30). Such a unique sample of extraordinary objects will enable a variety of follow-up sciences, and will therefore remain as a great legacy of the Herschel mission for years to come.
Lead Scientist: Eiichi Egami
Allocated time: 25 hours
A unique MIR/FIR signature of quenched star formation (SF) in early-type cluster galaxies has recently been discovered. This demise of active SF apparently imprints itself on the MIR (powered by SF) and FIR (powered in part by ISM radiation field) dust emission for a period of only ~few x 10^7yr. If true, this signature could be used as a marker of quenching SF and the location, hence mechanism(s) used to extinguish that final SF episode in cluster S0s, be determined. However, without FIR data it is unclear if this signature is from the lack of SF or unusually cold dust.
Our ongoing study of Abell 1882, a coalescing supergroup observed just prior to collapsing into a rich cluster, has uncovered a significant population of these galaxies. We request Herschel PACS and SPIRE observations of the supergroup Abell 1882 to validate the report of a unique MIR/FIR signature of star-formation quenching that is occurring in early-type galaxies. This 27.8hr Herschel proposal will add key knowledge to the formation process of S0 galaxies and for the member population as a whole, dust properties plus gas consumption time-scale in a supergroup in the act of forming a rich cluster.
Lead Scientist: Glenn Morrison
Allocated time: 5.1 hours
We have discovered extreme velocity [CII] 158 um line emission from the z = 1.2 hyper-luminous QSO PG 1206+459. The [CII] line emission is concentrated in twin lobes of emission roughly centered on the CO emission but displaced +/- 1500 km/s with respect to the CO line core. The mass traced in the [CII] line is quite large - about 5E9 M(solar) in each lobe or 13% of the total molecular gas mass in the host galaxy. We interpret this symmetric [CII] velocity structure as an outflow, likely driven by the AGN. The velocities of the [CII] lobes are larger than the escape velocity, so much of this material may leave the galaxy quenching both star formation and AGN activity, and transforming it into a "red-and-dead" passive galaxy. The CO line profile also shows a broad and blueshifted component that may represent an additional molecular component to the outflow, although a merger origin is also possible. In OT1 we were awarded 2.9 hours of PACS spectroscopy (not yet scheduled) to observe the [OI] 63 um, [OIII] 52 and 88 um, and [OIV] 26 um lines from the blue component of the line. Here we ask for an additional 10.2 hours of PACS time to widen our spectral scan to enclose the newly discovered (March 2011) red lobe and significantly improve our detection limit over the entire velocity range. These observations will be used to constrain the physical conditions, ionization structure, total mass, and radiative environment of the outflowing material using extinction-free probes. Our [CII] observations of PG1206 represent the first time that massive outflows have been detected in the [CII] line - a well established tracer of photodissociated molecular gas. The proposed Herschel observations will lay the groundwork for future studies of molecular outflows using [CII] and other far-IR lines in the early universe that will soon be possible with ALMA.
Lead Scientist: Gordon Stacey
Allocated time: 10.2 hours
Constraining the star-formation activity in very high-redshift clusters: Herschel observations of SpARCS clusters at z = 1.6
We propose deep PACS 110/160 micron imaging for two of the most distant rich clusters ever discovered at z=1.6. These spectroscopically confirmed clusters are drawn from the homogeneously selected Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS), and have impressive spectroscopic coverage (a total of 26 confirmed members) and extensive multi-wavelength follow-up data (UV-MIR). This epoch marks a crucial turning point in the star formation rate-density relation: limited studies have shown that star formation shifts toward higher densities at z~1, and even peaks in a z=1.6 cluster core, albeit only a single cluster at this distance has been observed in the IR until now. Moreover, MIPS imaging has already identified nine cluster members, confirming that dust enshrouded star formation is occurring in these dense fields. We will use the PACS/MIPS data, in combination with the extensive optical spectroscopy and photometry, to characterize the nature of IR-luminous galaxies in clusters at z=1.6. We will also measure the total star formation rate in these clusters, which will be used to study the effect of environment on galaxy formation at an exciting new redshift regime.
Lead Scientist: Gillian Wilson
Allocated time: 36.8 hours
Constraining the star-formation activity in 10 SpARCS clusters: star-formation in the densest regions at z =1
We propose deep PACS imaging at 110/160 microns of a unique sample of ten high-redshift galaxy clusters spanning 0.87<z<1.34. These rich clusters are drawn from the homogeneously selected Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS), and have impressive spectroscopic coverage (a total of 457 confirmed members) and extensive multi-wavelength follow-up data (UV-MIR). These clusters bridge a pivotal epoch when star formation shifts toward higher densities and when substantial cluster mass is assembled. Moreover, MIPS imaging has already identified 55 cluster members, confirming that dust enshrouded star formation is occurring in these dense fields. We will use the PACS/MIPS data, in combination with the extensive optical spectroscopy and photometry, to characterize the nature of IR-luminous galaxies in clusters at z~1. We will also measure the total star formation rate in these clusters, which will be used to study the effect of environment on galaxy formation.
Lead Scientist: Gillian Wilson
Allocated time: 25.6 hours
We propose Herschel-SPIRE imaging of a 14'x14' field (corresponding to 7.1 Mpc x 7.1 Mpc) around the recently discovered cluster CL1449+0856 at redshift z=2.07. This structure is the most distant X-ray luminous galaxy cluster known to date, traced by a strong overdensity of red compact galaxies. Up to now, we securely identified 21 cluster members and our Spitzer-MIPS 24micron observations reveal a very high degree of star-forming activity in the cluster core. With our SPIRE imaging, we aim to reveal obscured star-formation activity within and around this evolved galaxy cluster as expected around a rapidly assembling high-z halo, as already indicated by our very recently obtained APEX-LABOCA imaging. We will search for massive dusty starbursts as cluster members, identify and characterize the counterparts of LABOCA SMGs, determine SEDs and dust temperatures of our sources and compare the properties of our IR-bright cluster members with SMGs in blank fields. This project will push the study of massive dusty starbursts in established clusters to the highest possible redshifts.
Lead Scientist: Helmut Dannerbauer
Allocated time: 3.9 hours
The Planck mission has the unique capability of finding systematically and on the whole sky the rarest, most luminous high redshift submm sources. These can be lensed objects or proto-groups/clusters of galaxies containing many individual sources forming stars at very high rates. Our full sample of candidates contains about 1 source per 30 sq. deg., and already 3 candidates have been confirmed as interesting high-z sources: one was found to be a proto-group at z~3, based on a SPIRE OT1 pilot project; and 2 others are z~3-4.6 sources already found in the H-ATLAS and around A773. We now propose to use SPIRE to image a larger set of Planck sources to obtain a statistically significant sample of 70 high-z proto-groups and clusters. This will give new insights into the early evolution of galaxies in the highest density regions, improving our understanding of the relationship between the growth of structures and star-formation, and placing constraints on the level of non-Gaussianity within the LCDM model. This program exploits the exceptional synergy and complementarity between Planck and Herschel.
Lead Scientist: Herve Dole
Allocated time: 16.3 hours
Using the WISE Preliminary Data Release mid-infrared and UKIDSS near-infrared catalogs, we have identified a sample of 0.8<z<1.5 infrared-bright galaxies with extremely large 9.7 micron silicate absorptions (~ 5 magnitudes). These highly obscured sources present a small but not well determined fraction of the whole ULIRG population, possibly representing one the earliest stages in the transition from star formation to black hole accretion domination, before the concealing gas and dust is expelled from the galaxy. From over 1200 square degrees and 1.6 million 12-micron sources, we extracted 230 extreme silicate absorbers, increasing the sample of known extreme silicate absorption sources by more than an order of magnitude from the mere handful (~5) now known. We propose to obtain 70, 100, and 160 micron PACS imaging of a sub-sample of 45 for which we have spectroscopic redshifts. This will allow us to measure and characterize the peak of the infrared emission providing total bolometric luminosities and allowing a full decomposition of the contributions of hot, warm, and cool dust within these extreme sources. We will also measure their mid-infrared continuum slope, critical for an accurate measurement of the depth of the silicate absorption feature. Combined with hot dust emission, the strength of the silicate absorption will put strong constraints on the size of emitting region.
Lead Scientist: James Colbert
Allocated time: 12.7 hours
We propose to use PACS and SPIRE in parallel mode to map about 45 sq deg of the nearby Fornax galaxy cluster. Our science objectives are mainly concerned with evolutionary processes within the cluster environment. Specifically we will derive FIR/sub-mm luminosity functions, construct complete spectral energy distributions, search for cold dust in the outskirts of galaxies and in the intra-galactic medium and consider and compared the properties early type and dwarf galaxies that are prolific within the cluster environment. The total time requested is 93.2 hours.
Lead Scientist: Jonathan Davies
Allocated time: 31.1 hours
A Herschel SPIRE study of star-formation in the host galaxies of the most luminous high-redshift quasars
We propose to use this final Herschel call to obtain SPIRE 250,350,500 micron images of a sample of nearly 300 of the most luminous quasars to have ever existed in the universe. Our proposed programme samples the top decade of quasar optical luminosities, over the key redshift range 2.5 < z < 4.5, which corresponds essentially to the 1-2 Gyr epoch over which such objects are found. This regime has been neglected by current Herschel programmes, and our targets are too rare on the sky for more than a handful to be contained within the existing/planned Herschel SPIRE surveys. Via careful sample construction, including matched sub-samples of radio-loud and radio-quiet SDSS quasars, we aim to determine how dust-enshrouded star-formation activity in the host galaxies of these super-massive active black holes depends on their redshifts, and their optical/radio power. This will allow fundamental tests of the proposed linkage between galaxy and black-hole growth, and possible modes of feedback which seem to be required to shut down star formation in massive galaxies at these high redshifts. We believe it would be a major missed opportunity if Herschel is not used to assemble a legacy dataset for these, the presumed progenitors of today's most massive galaxies, especially since the data from this (relatively inexpensive) programme can ultimately be combined with comparable statistics on lower-luminosity quasars from the major SPIRE surveys such as H-ATLAS and HerMES (thus providing excellent coverage of the luminosity-redshift plane). Finally, since our quasar targets should mark some of the highest density regions in the young universe, we will explore the 12 sq arcmin sampled by Small-Map mode around each quasar to quantify the evidence for enhanced star-formation activity in the general vicinity of these quasar hosts, as anticipated if we are observing the progenitors of today's massive galaxy clusters.
Lead Scientist: James Dunlop
Allocated time: 58.3 hours
We propose an experiment to investigate the evolution of the most massive galaxies that reside in the cores of massive clusters today. We aim to catch their progenitors - gas-rich, intensely starbursting galaxies - in the act of accretion onto massive halos at z~1. Our survey is unique because we will map a super-cluster environment that is in the throes of a spectacular 3-way merger, allowing us to examine the astrophysics of galaxy evolution during a key stage of the hierarchical build-up of large scale structure. Our target - RCS 2319 - is a system of three ~5x10^14 M_Sun galaxy clusters at z=0.9 separated by just 3 Mpc. RCS 2319 is the progenitor of a >10^15 M_Sun cluster, and the ideal target to examine the complex relationship between the formation of massive galaxies and the dense, dynamic environments they inhabit. We will obtain a deep map of RCS 2319 with SPIRE, covering a projected extent of 14x14 Mpc, including the full range of sub-environments from the dense cores out to the group-scale and filamentary structure in the super-cluster outskirts. Our goals are to (i) identify ULIRG-class (>10^12 L_Sun) cluster members and investigate their properties in the context of the super-cluster environment; and (ii) calculate the cross-power spectrum of FIR emission with galaxy surface density, allowing us to search for statistical correlations between obscured star formation and environment beyond the confusion limit.
Lead Scientist: James Geach
Allocated time: 8.2 hours
Large-area, multi-wavelength surveys from the ground and space have discovered a new population of strongly lensed, dusty, star-forming galaxies (DSFGs). These sources have lensing magnifications of x10-50 and present an exciting new means of studying otherwise faint high-redshift contributors to the cosmic infrared background (CIB) in exquisite detail. With its large survey area and long-wavelength selection, the South Pole Telescope (SPT) selects the rarest, brightest, and most interesting sample the sample of strongly lensed DSFGs and is enabling major advances in our understanding of massive galaxy formation.
Here we request 16.9 hours of SPIRE and PACS imaging to followup a sample of 88 sources from a 1.4 mm flux-limited sample with the aim of constraining SEDs to 1) estimate photometric redshifts, 2) measure dust temperatures, 3) derive the apparent and intrinsic IR luminosities, and 4) accurately determine molecular and atomic line to luminosity ratios. This proposal is part of a systematic followup campaign which includes approved and ongoing programs with HST, VLT, Spitzer, APEX, ATCA, and ALMA early science observations.
Lead Scientist: Joaquin Vieira
Allocated time: 16.5 hours
Little is known about the redshifted FIR properties of the 1.2mm selected sample of high-redshift, dusty starburst galaxies. Constraints on the dust temperature and total FIR luminosity depend on observations at short submm-wavelengths, which are only now possible with BLAST and Herschel. We have mapped a 0.5 square degree field at 1.2mm with MAMBO, centered on the Abell 2125 cluster. Complementary deep 1.4GHz radio imaging from the VLA has allowed us to identify radio counterparts to 83% of the 1.2mm selected galaxies, making this the largest sample of starburst galaxies selected at this wavelength with robust radio counterparts. We request 5.2 hours with PACS and 2.0 hours with SPIRE to map this field over the same area covered by MAMBO. These data will provide the first constraints on the (rest-frame) FIR spectral energy distribution of such a complete sample of 1.2mm selected starbursts.
Lead Scientist: Jeff Wagg
Allocated time: 7.2 hours
Revealing the ISM in high redshift galaxies: Herschel PACS observations of gravitationally lensed SMGs
Little is currently known about the dominant mode of star-formation in high-redshift submillimeter-bright galaxies (SMGs), their relation to local ULIRGs and the contribution of AGN to their immense far-infrared (IR) luminosities. Observationally, the physical conditions in these sources are difficult to constrain because the most active regions are also the most highly obscured, and thus can only be probed with mid- and far-IR data. At high redshifts the PACS wavelength coverage is ideally suited to target critical fine structure emission lines from species including oxygen, nitrogen and silicon, and rotational transitions from molecular hydrogen. The relative fluxes of these emission lines, in combination with accurate far-IR luminosities, can be used to constrain the physical conditions in the ISM, such as the density and the ionization state, which in turn provides information about the star-formation triggers and AGN activity. However, most high-redshift galaxies are too faint for these emission lines to be detected, and therefore, studies of the high-redshift ISM are rare. We request Herschel PACS spectroscopy, and 70 and 160um photometry of 13 high-redshift (z~1 to 3), far-IR luminous, gravitationally lensed galaxies. These sources are unique -- the flux boosting from gravitational lensing means that it is feasible to observe them with Herschel, and they all have exceptional ancillary data which complements the proposed program and will maximise the science output from this project. Targets are selected from the H-ATLAS and HerMES surveys and comprise a complete sample of bright lensed SMGs with confirmed CO redshifts. The PACS photometry will constrain the far-IR SEDs, and identify any warm dust (i.e. AGN) components. The spectroscopy will be used to characterize the ISM in these sources, and will double the number of high-redshift galaxies for which such analysis is currently possible. We request a total of 78.9 hours for PACS spectroscopy (73.0 hours) and photometry (5.9 hours) of 13 sources.
Lead Scientist: Julie Wardlow
Allocated time: 78.9 hours
Gamma-Ray Bursts (GRBs) are so luminous that they can shine through highly obscured galaxies, nearby and in the remote universe. GRBs enable identification of galaxies independently of their luminosity, thus singling out a population that is a potentially powerful probe of galaxy evolution. Here we propose PACS and SPIRE imaging of the host galaxies of dark GRBs, GRBs whose optical afterglow emission is weaker than expected relative to Xrays. Recent work suggests that the main cause of the optical darkness of a GRB is dust extinction and moderate redshift, and their hosts may be a significant component of the GRB host galaxy (GRBH) population at redshifts > 1. Our sample of 13 dark GRBHs has been carefully selected by requiring a prior Spitzer detection, so that we will be ensured of detecting the far-IR emission with Herschel. We already have collected a large amount of ancillary multiwavelength data which will be combined with the Herschel photometry to construct spectral energy distributions (SEDs) from the UV to the far-IR. Fitting SEDs with a library of galaxy templates will enable us to derive bolometric luminosities and SFRs, constrain dust mass, dust temperature, and grain properties, as well as stellar age and mass. We will compare the dust and stellar components of the galaxies, and analyze the GRBHs in the context of other high-z galaxy populations. Such a program is now possible thanks to the unique ability of Herschel to study dust emission in galaxies over a wide range of redshifts. Ultimately our proposed study of GRBHs will open a new window on the study of galaxy formation and evolution.
Lead Scientist: Leslie Hunt
Allocated time: 25.4 hours
The Physical Conditions of the Interstellar Medium in a Molecular Einstein Ring Submillimeter Galaxy at z~4
Understanding the nature of the most distant starburst galaxies, in particular submillimeter galaxies (SMGs), has been one of the major challenges of modern observational cosmology. However, the intrinsic faintness, heavy obscuration and large cosmological distances of these systems have precluded the characterization of their optical properties and have limited their study to the rarest starburst galaxies. The most efficient way to investigate the properties of these systems is with the aid of gravitationally lensing at IR wavelengths. The recent discovery of a bright, highly magnified (m~12) SMG, MM18423+5939 at z~4, represents an unprecedented opportunity to understand in detail the interstellar medium (ISM) conditions in these objects and to bring such studies to a new level of detail. Follow-up observations with the EVLA showed that this source forms a spectacular molecular Einstein ring in CO high-resolution images, the second such object known to date. Here, we request 29.6 hrs of Herschel/SPIRE time to simultaneously observe, for the first time, three of the main coolants of the ISM: the O[I]63um, O[III]52um and O[III]88um emission lines, in a SMG at z~4. We will obtain a direct measurement of the physical state of the dense and warm gas phase that will be directly comparable to similar observations of local galaxies. We will combine these measurements with previous CO/[CI] observations of our target to provide a critical, detailed model of its ISM gas properties namely temperatures, H2 densities, e- densities and UV radiation field. Our on-going HST/WFC3 imaging program of our target is key, since it will allow us to accurately model the lens and source-plane gas distribution for a proper interpretation of the line emission. With a total IR luminosity of 1.3x10^14/m L_sun, this source has the potential to become the archetype for future deep spectroscopy with ALMA and dense gas studies at high-redshift.
Lead Scientist: Manuel Aravena
Allocated time: 29.6 hours
The recent detection of large amounts of molecular gas in a sample of "normal" star−forming galaxies at z~1.5 has opened up a unique window into the study of the population of galaxies that dominates the star formation rate density of the Universe. Here, we propose pioneering PACS observations of the [OI]63um emission line in the best studied sample of four such galaxies that will allow us to carry out an unprecedented characterization of their star-forming properties. We aim to characterize the warm and dense neutral gas, in combination with our CO and FIR luminosity measurements, by comparing with radiative transfer models of the interstellar medium. We will be able to study the possible relation between the [OI] line and their main physical parameters (star formation rate, star formation efficiency, masses). Herschel is the only observatory capable of performing this kind of observations, that are forbidden to ground based observatories. We request a total of 32.63h of Herschel/PACS time toprovide the last piece in the puzzle that will permit to disentangle the properties on what appear to be the progenitors of galaxies like the Milky−Way.
Lead Scientist: Manuel Aravena
Allocated time: 32.6 hours
Herschel+CANDELS: Unraveling the physical processes that regulate star formation and AGN activity in ordinary galaxies at z=2
The deepest Herschel surveys have established a distinction between steady "main sequence" star formation, whose rate is closely tied to galaxy mass at a given redshift, and elevated starburst activity in ordinary, L*(IR) galaxies at z > 1.5. They have also shown that supermassive black hole growth occurs mainly through secular processes in these main sequence galaxies, and have revealed otherwise obscured AGN missed by the deepest X-ray surveys. However, the physical processes that trigger starbursts, and the relation between star formation, AGN activity, and the structural properties of galaxies at this peak era of galaxy growth, are far from clear. We propose a survey to address these questions by measuring far-infrared luminosities and star formation rates for a large sample of high redshift galaxies with deep, high-resolution near-infrared imaging from the CANDELS HST WFC3 Treasury program. Herschel PACS and SPIRE observations deep enough to detect 700+ L*(IR) galaxies at z > 1.5 will be obtained for the five CANDELS fields and correlated with the detailed morphological and structural properties that only HST/WFC3 imaging can provide. We will establish whether interactions and mergers drive starburst activity, and examine their relevance for fueling AGN activity. The improved statistics will allow a definitive measure of the space density of L*(IR) galaxies at z=2, a basic (and currently very uncertain) demographic quantity for the history of cosmic star formation. The survey will provide a legacy of targets for detailed investigation with ALMA, tripling (beyond GOODS-South alone) the number of ALMA-accessible fields with the deepest Herschel data.
Lead Scientist: Mark Dickinson
Allocated time: 193.6 hours
We propose to obtain deep IR imaging at 70um, 100um, and 160um with PACS (3.4h), and PACS spectroscopy of the [C II] 158um line (3.4h) for the anomalous galaxy cluster Abell 2029. This cluster has similar properties to both cool core (low central entropy, UV emission, radio-loud) and non-cool core (no measurable cooling in X-ray, no detectable H-alpha or CO) clusters, suggesting that it may be a transition object. The presence of young stars, inferred by extended UV emission, coupled with the absence of H-alpha emission, is evidence for a recent (~10 Myr) starburst. The missing piece to this puzzle is the mid-far IR, which is the only wavelength range that has not been well studied in this system. The addition of deep mid-far IR photometry will allow us to i) confirm/disprove the presence of a young stellar population, and ii) infer a starburst age based on the dust temperature. Deep IR spectroscopy of the [C II] will probe for a hidden reservoir of cool gas and would provide an estimate of the cooling rate at lower temperatures. Combined, these observations will shed new light on a galaxy cluster that, despite its proximity and the availability of deep, multi-wavelength data, has long defied understanding.
Lead Scientist: Michael McDonald
Allocated time: 6.8 hours
We propose Herschel spectroscopic observations of the [C II]158 um and [O I]63 um emission lines in 4 extremely bright, lensed, high-redshift galaxies. Herschel photometric surveys conducted toward galaxy clusters have identified these highly magnified sources, which would otherwise be undetectable below the confusion limit of the instrument. These exceptional targets provide the unique opportunity to study the characteristics of the ISM in typical galaxies with moderate luminosities at high redshift.
Recent studies have identified key differences between the far-infrared properties of local LIRGS/ULIRGS and galaxies of comparable luminosity at high redshift. However, the highest redshift observations are inherently biased toward more luminous galaxies, making it difficult to extend this comparison to the abundant population which is intrinsically faint. Herschel spectroscopy of highly magnified galaxies provides the only means to probe the physical conditions within this more typical population. Measurements of the [C II] and [O I] cooling lines are sensitive to the temperature and density of the gas surrounding star−forming regions, as well as the strength of the incident far ultraviolet radiation from starbursts. These observations will provide insight into the environmental conditions that drive the differences between high-redshift star-forming galaxies and those in the local universe.
Lead Scientist: Marie Rex
Allocated time: 6.6 hours
A substantial fraction of the star-formation history of the Universe is encoded in the cosmic infrared background (CIB), but fundamental issues about the sources which make up the CIB such as their redshift distribution, their stellar masses, and the masses of their host halos remain poorly constrained by current measurements. To address these issues, we propose the Herschel Redshift Survey (HeRS), a 70 deg2 SPIRE survey in the SDSS Stripe 82. HeRS is designed to leverage the unprecedented spectroscopic redshift and stellar mass catalogs of the Hobby Eberly Telescope Dark Energy Experiment (HETDEX) and Spitzer-HETDEX Exploratory Large Area (SHELA) Survey, in order to provide the most precise constraints yet obtained on the obscured star-formation properties of galaxies in the redshift range 1.8 < z < 3.5. HeRS will principally target two goals: i) the redshift distribution of the infrared light that makes up the cosmic infrared background; and ii) the evolution of the specific star-formation rate of galaxies as a function of redshift. Our measurements will far outstrip any that could be made with existing or planned SPIRE surveys because the high level of confusion noise (3–30 times higher than the signal) requires cross-correlating maps with the highest quality ancillary data: specifically, data that provides extremely accurate redshifts and reliable stellar mass estimates over a wide area. And only HETDEX spectroscopic redshifts are capable of measuring the density field and bias to the required 1–2% accuracy. These measurements will break the luminosity/redshift degeneracy plaguing the interpretation of correlation studies of the CIB, and place tight constraints on source population models. This observing cycle represents the last chance to obtain Herschel observations of what will be one of the premier cosmological fields for years to come.
Lead Scientist: Marco Viero
Allocated time: 34.7 hours
We propose to measure relativistic corrections to the Sunyaev-Zel'dovich effect (rSZ) in two clusters of galaxies with SPIRE-FTS, providing measurements of the intra-cluster medium (ICM) temperature with ~30 arcsec spatial resolution. For the first time, these measurements will enable: 1) unambiguous, high significance measurement of the rSZ correction, and 2) precise determination of the temperature substructure of extremely hot clusters. Both measurements are technically feasible with SPIRE-FTS and are inaccessible in any other way. The value our proposed observations for demonstrating the ability to measure the temperature of ICM substructures in massive, complex clusters is enormous, both for cosmological applications (i.e. a precise and unbiased determination of the total mass of clusters) and for astrophysical applications (untangling the complex atmosphere of clusters using SZ). These measurements will prove that measurements of the rSZ correction can enable important new studies of cluster physics and the fleeting opportunity to make them should not be missed.
Lead Scientist: Michael Zemcov
Allocated time: 13.7 hours
We propose PACS photometry to constrain the rest frame infrared (15-40um) properties of six 4.5<z<5.3 spectroscopically confirmed extreme starbursts (sub-mm) galaxies, tripling the sample size of well studied galaxies at z>4. This will allow us to: 1) Obtain accurate total infrared luminosity measurements for these sources resulting in an unbiased measure of star formation at z~5; 2) Determine the relative contribution of Active Galactic Nuclie (AGN) and star formation to the total infrared luminosity; 3) Characterize the amount of warm dust emission in these galaxies and compare it to their gas properties; 4) Create templates for "typical" z~5 extreme starburst (sub-mm) galaxies to inform theoretical exploration and enable photometric searches for larger samples of objects. The existing 110um and 160um PACS survey data are not deep enough to fully constrain the infrared spectral energy distributions are crucial to confirm the nature of these systems and provide tight constraints on models for dust formation in the early universe.
Lead Scientist: Peter Capak
Allocated time: 37.1 hours
PACS spectroscopy of the Spiderweb radio galaxy (PKS 1138-26) at redshift z=2.156 will be used to study jet-shocked molecular and atomic gas in a rapidly evolving protocluster central galaxy. This will lead to a better understanding of the impact of AGN feedback on the evolution of massive elliptical galaxies in general. We have detected extremely luminous (7E10 Lsun) H2 0-0 S(3) emission in a deep Spitzer IRS spectroscopic map. This is by far (a factor of 50) the most luminous known molecular hydrogen emission galaxy. We estimate that there must be >1E7 Msun of warm (T=650 K) molecular gas heated by dissipation of kinetic energy from the relativistic radio jet. PACS spectroscopy of the H2 0-0 S(0) line will enable us to measure the mass of warm H2 at lower temperature (T=100-500) K, which likely constitutes the bulk of the shocked molecular gas, possibly >1E11 solar masses. We have also detected ultraluminous PAH emission indicating a star formation rate of 1000 Msun/yr. PACS spectroscopy of the [Si II] 35 micron and [O I] 63 micron cooling lines will provide additional diagnostics of the shocked neutral medium, including distinguishing between magnetic and nonmagnetic shocks, and assessing the kinematics of this important ISM component in a massive elliptical galaxy under construction.
Lead Scientist: Patrick Ogle
Allocated time: 14.8 hours
We propose observations in the two reddest PACS and all three SPIRE bands of the host galaxies of a sample of five GRBs. The sample was carefully selected based on the detection of large extinction in the GROND SED of the GRB afterglow, and all hosts have a large amount of multiwavelength data in hand, including sensitive submm observations. Together with the Herschel data, we will model the SEDs from the UV to the submm with the broadband galaxy SED fitting software, CIGALE, to derive bolometric luminosities and SFRs, and constrain dust mass and dust temperature. We will compare the dust properties of the whole galaxy with that derived from the GRB afterglow to constrain the dust clumpiness (covering fraction, total extinction). We will also compare the dust and stellar components of the galaxies, and investigate the GRB hosts in the context of other high-z galaxies. The Herschel data will provide indispensable observations of the peak of the thermal dust emission component, which accompanied with our APEX and SCUBA submm observations will provide the most accurate measurements to date of the extinction and emission properties of dust within GRB host galaxies.
Lead Scientist: Patricia Schady
Allocated time: 6.2 hours
We propose Herschel PACS mapping of the central 64 square Mpc around the massive galaxy cluster MS0451 (at z=0.54) to determine the dominant physical mechanisms that trigger and quench star formation in galaxies over a wide dynamic range of local environments. MS0451 is one of the most massive, X-ray luminous clusters known, and previous studies of galaxies within the virial radius of MS0451 have found strong evidence for abrupt quenching of star formation, likely due to ram-pressure stripping by the hot intra-cluster medium (Geach et al. 2006, Moran et al. 2007). Studies focusing only on the cluster core are not sensitive to transformative effects that can begin to alter the morphology, color, and star formation rate (SFR) of galaxies on the cluster outskirts. Our observations will allow for robust measurements of star formation rates as low as ~30Msun/yr for galaxies out to ~2Rvir, and will give a more complete picture of the effect of environment on the evolution of galaxies via triggering and quenching of their star formation.
Lead Scientist: Ryan Cybulski
Allocated time: 27.9 hours
Understanding how massive black holes, galaxies and clusters of galaxies jointly emerged from inhomogeneities in the primeval Universe is one of the most compelling objectives of modern observational astrophysics. Here we propose to use SPIRE's excellent sensitivity and survey speed to obtain for the first time a significant sample of proto-clusters over the key redshift range 2 < z < 4. This would be done through imaging of fields centered at AGN selected to harbour the most massive black hole. The resulting data set will allow us to address key questions, including: (i) Are the most massive black holes at z > 2 located in the largest and most massive proto-clusters? (ii) What are the masses, sizes, total star formation rates and velocity dispersions of the protoclusters? (iii) What are the masses, ages and star formation rates of the individual proto-cluster galaxies? Do we see a spatial segregation of galaxies with different masses or star formation rates? (iv) Do the properties of the proto-clusters and their galaxies evolve with redshift? (v) Are the galaxies in these proto-clusters older, larger and more massive then field galaxies?
Lead Scientist: Rottgering Huub
Allocated time: 21.6 hours
Herschel-GAMA: Gas-fuelling, Feedback and Star-Formation in Galaxy Groups in the Local Volume
Under the Cold Dark Matter paradigm the propensity of intergalactic baryons to cool and accrete onto existing galaxies or form new galaxies depends both on the mass of the inhabited dark matter halo through the process of virialisation, as well as on the mass, dynamical state and gas content of individual galaxies, since the latter can either enhance or hinder accretion though so-called feedback from starformation or AGN activity. We have used the unprecedented density of redshifts furnished by the Galaxy And Mass Assembly (GAMA) deep wide field spectroscopic survey to identify the first statistically significant sample of low mass groups, opening the way for deep pointed multiwavelength investigations to probe baryonic processes over a more representative population of haloes than previously possible. Here we propose deep pointed miniscan exposures with PACS at 70, 110 and 160 microns of a representative subsample of 57 low-mass blue sequence member galaxies of GAMA groups with z less than 0.04 spanning a range in dynamical mass between 10^11 and 7.10^13 M_solar and a range in galaxian stellar masses from 10^8.0 to 10^9.25, parameter space that has not yet been surveyed in the FIR. Combining this with corresponding multiwavelength data on existing blind surveys covering the GAMA footprint and deep surveys of massive clusters, we will provide a complete picture of the UV-FIR/submm emission from blue sequence galaxies spanning four orders of magnitude in host halo mass and three orders of magnitude in stellar mass. This will provide a comprehensive picture of the variation of present day SF activity with environment which will serve as a fundamental empirical constraint on the baryonic processes determining the relation of our visual perception of the Universe to its underlying DM structure.
Lead Scientist: Richard Tuffs
Allocated time: 25 hours
We propose to use PACS to observe the forbidden fine-structure line [OI]63μm, and for six of the sources, the [OIII]88μm line, in a sample of 16 Herschel-SPIRE selected ULIRGs, spectroscopically confirmed at z = 1−2 (keeping [OI] in the PACS-spectrometer band). We have further chosen the sources to lie in a single southern field in order to exploit the synergy with ALMA, to provide additional line diagnostics, and to emphasize the advantage of gaining insight into an unlensed galaxy population, both from environmental effects, and to avoid the differential lensing bias which can plague line ratio diagnostics. This represents a unique sample of objects made possible only with the advent of SPIRE ULIRG selection at high−z, and importantly filling a void in existing or planned similar observations with PACS; an allocated program in OT1 (in the same field) focussed on a small sample of 870μm selected SMGs, lying mostly at z = 1.0–1.3 with a few AGN-dominated systems at z = 1.3–2.0. Our targets (which don’t overlap) will complement this sample of sources in the same cosmic volume.
Lead Scientist: scott chapman
Allocated time: 24.9 hours
We request 59.8 hours of Herschel time to observe 20 normal star-forming galaxies in the [CII] 158 micron and [OI] 63 micron lines. These galaxies lie at high redshift (1<z<3). They are highly magnified by gravitational lensing, but have modest star formation rates. Therefore they represent our best chance of studying star formation and the interstellar medium in typical, common galaxies at this epoch. Redshift 1 to 3 spans the peak of both star formation activity and black hole accretion in active galactic nuclei-- a period that was crucial in shaping our modern universe. Most of this redshift range is inaccesible to ground-based observations of [CII], [OI], or both. Herschel offers the unique opportunity to study both lines with high sensitivity throughout this epoch (using HIFI for [CII] and PACS for [OI]). These two lines are the main cooling lines of the atomic medium. By measuring their fluxes, we will measure (1) the cooling efficiency of gas, (2) gas densities and temperatures near star−forming regions, and (3) gas pressures, which are important to drive the winds that provide feedback to star−formation processes. By combining the proposed observations with existing multiwavelength data on these objects, we will obtain as complete a picture of galaxy-scale star formation and ISM physical conditions at high redshifts as we have at z=0. Then perhaps we can understand why star formation and AGN activity peaked at this epoch. In Herschel cycle OT1, 49 high redshift IR luminous galaxies were approved for spectroscopy, but only two so-called normal galaxies were included. This is an imbalance that should be corrected, to balance Herschel's legacy.
Lead Scientist: Sangeeta Malhotra
Allocated time: 59.8 hours
We propose to address the impact of a major merging event on star formation on the bullet-like cluster: Abell 2163. This very massive cluster, among the most luminous and hottest clusters observed in X-Ray, shows outstanding properties from X-ray to radio wavelengths. Thanks to an extensived combined Xray/optical/weak-lensing program, we have recently reconstructed the merging history of this cluster (Maurogordato et al. 2008, Bourdin et al. 2011, Okabe et al. 2011) showing definitively the occurence of a recent major merger (< 0.5 Gyr) with a fast moving gas core spatially segregated from galaxies and dark matter. Suggesting an efficient stripping of the gas core by ram pressure (Okabe et al. 2011) such a clear spatial segregation has been detected so far in very few massive clusters, the most spectacular one being 1E 0657-56, the so-called"bullet cluster". A2163, at z=0.2, is the nearest one, making it an excellent target to address in details the effect of ram pressure induced by a major merger event. Besides the "bullet" in the central region, Abell 2163 shows a filamentary complex, embedding several groups and a sub-cluster being accreted along the filament, making it also a very interesting environment to address the efficiency of galaxy pre-processing in groups and filamentary structures. We propose to perform observations of A2163 with Herschel using PACS (100 and 160 microns: 12.7h) and SPIRE (250, 350 and 500 microns: 1.3 h), requesting a total time of 14.0h. Together with extensive ancillary data on this cluster, these observations will allow us to perform good estimates of star formation rates, and recover the stellar masses and star formation histories of cluster galaxies. These will be used to test the impact of the cluster merger event and its large scale environment on star formation.
Lead Scientist: Sophie Maurogordato
Allocated time: 14 hours
Long gamma-ray bursts (LGRBs), are the brightest transient events in the Universe. This, combined with their wide range in redshift and the fact that they are associated with the collapse of massive, low metallicity stars, establishes LGRBs as powerful probes of star formation and an unbiased method for identifying high redshift galaxies. However, due to biases in the detection of the optical emission associated with LGRBs and lack of host measurements at infrared wavelengths, it is currently unclear whether we have a representative picture of the LGRB host galaxy population. In particular, there is tentative evidence to suggest that a significant fraction of LGRB hosts are dusty and hence luminous in the infrared, an issue which can be settled uniquely with Herschel. Here we propose the first statistical study of LGRB host galaxies with Herschel/SPIRE, requesting 25 hrs of observations. Our sample of 100 LGRB host galaxies have a redshift distribution which peaks at z=2.0 and are split 50:50 into dark and bright, these classifications referring to the strength of the optical afterglow emission following the LGRB. Although, we expect a significant fraction (>20%) of the sample to be individually detected in SPIRE enabling more detailed examination of these sources, we plan to obtain a representative view of the dust properties of LGRB hosts by stacking the SPIRE images of the bright and dark sub-samples. The SPIRE bands will probe the peak of the dust emission over most of the redshift range covered by our sample, enabling us to determing average and representative measurements of the dust content, infrared luminosity, star-formation rate, dust mass/temperature and extinction for LGRB hosts. Our proposed observations are the only opportunity to compare the global dust properties of bright and dark LGRB hosts, with the results from our study having important implications in LGRB theory and LGRB progenitor models.
Lead Scientist: Samantha Oates
Allocated time: 25 hours
THE HERSCHEL-AKARI NEP DEEP SURVEY: the cosmological history of stellar mass assembly and black hole accretion
We propose a far-IR and submm mapping survey of the premier AKARI deep field in the North Ecliptic Pole, in PACS/SPIRE parallel mode. This is the only major deep infrared field not yet covered by Herschel guaranteed or open time key projects. The outstanding and unparalleled continuous mid-IR photometric coverage from AKARI, far better than equivalent Spitzer surveys, enables a wide range of galaxy evolution diagnostics unachievable in any other survey field (including Herschel HerMES/PEP fields), by spanning the wavelengths of redshifted PAH and silicate features and the peak energy output of AGN dust tori. The investment by AKARI in the NEP represents ~10 percent of the entire pointed observations available throughout the lifetime of AKARI. Our proposal remedies the remarkable omission from Herschel's legacy surveys of the premier extragalactic deep field from another IR space telescope.
We will simultaneously identify and find photometric redshifts for the Herschel point source population, make stacking analysis detections of the galaxies which dominate the submm extragalactic background light as a function of redshift, determine the bolometric power outputs of the galaxies that dominate the submm background, compare the UV/optical/mid-IR continuum/PAH/far-IR/submm/radio star formation rate estimator in the most comprehensive IR survey data set to date, and track the coupled stellar mass assembly and black hole accretion throughout most of the history of the Universe.
In OT1 the HOTAC concluded "The science output from the proposed survey will be outstanding [...] The panel was convinced that these observations should be done" but it since became clear that priority 2 time is very unlikely to be executed, so we request reclassification to priority 1.
Lead Scientist: Stephen Serjeant
Allocated time: 6.2 hours
Dust in the wind: the role of dust in ram-pressure stripped gas and intracluster star formation (Part II)
We propose to detect dust associated with ram−pressure stripping through deep Herschel PACS/SPIRE imaging of a carefully chosen set of cluster galaxies that show strong signs of on−going stripping and intracluster star formation. This is a continuation of our OT1 program where we have successfully detected a dust tail caused by ram-pressure stripping in the one case where we have obtained a complete PACS/SPIRE photometer dataset. Our highest priority OT1 targets have not been observed, and our original sample was small, consisting of only five galaxies. Based on our current success, we have further refined our selection criteria to only choose galaxies within the high pressure cluster environment that show signs of intracluster star formation primarily due to ram-pressure stripping of gas. Our program will carry out deep Herschel observations of six galaxies that have highly extended (~20−80 kpc) UV and H_alpha tails associated with intracluster star formation. Herschel is the only telescope that has the sensitivity to detect the emission from dust blown out into the intracluster medium (ICM). With our proposed observations we aim to: 1. quantify the temperature, mass, and lifetime of dust blown out into (or formed in-situ within) the ICM; 2. understand the role dust plays in the existence of molecular hydrogen in the ICM and intracluster star formation. The Herschel observations will expand our already large multi−wavelength dataset and finally provide complete inventory of the gas and dust associated with ram−pressure stripping, so we can study the effects of ram−pressure on galaxy evolution. This will be the last opportunity in a very long time to make these measurements.
Lead Scientist: Suresh Sivanandam
Allocated time: 12.5 hours
High redshift radio galaxies (HzRGs) are the most dramatic examples of the formation of massive galaxies in the early Universe, as evidenced by their extreme (>1000Msun/yr) star formation rates. At the same time they coincide with a phase of rapid coeval black hole (BH) growth, as revealed by their powerful active galactic nuclei (AGN). This makes HzRGs unique laboratories in which to study the coevolution of massive galaxies and their central BHs. Our team has successfully carried out comprehensive imaging surveys of 62 powerful HzRGs at z > 1 using Spitzer and Herschel. These surveys have demonstrated that HzRGs have high stellar masses (>1e11Msun), and mid-IR AGN luminosities comparable to the most powerful QSOs known. Also, they have allowed us to separate the AGN and starburst contributions to the total IR luminosity. In parallel to this, we are undertaking a large CO(1-0) line survey towards a subset of 10 HzRGs using ATCA, which will provide us with excitation-unbiased mass estimates of the total molecular gas available for star formation. With this proposal we will constrain the bulk physical conditions of the star forming gas in HzRGs using the far-infrared OI fine-structure line at 63micron, which is one of the brightest diagnostic lines of the interstellar medium (ISM) in galaxies. The [OI] line, which can contain as much as >0.1% of the total IR luminosity of a galaxy, is one of the major coolants of the ISM, and is expected to be particular bright in the type of dense, hot, star forming gas expected to dominate the ISM in HzRGs. Utilizing our accurate IR luminosity estimates and molecular gas masses in combination with [OI] we will employ photo-dissociation models to constrain the gas density and the impinging FUV radiation field. We request a total of 13.1hrs of PACS spectroscopy (~2.2hrs per source, ensuring a S/N > 5) in order to detect the [OI] line towards six carefully chosen HzRG, representative of the luminous 1 < z < 2.3 radio galaxy population.
Lead Scientist: Thomas Greve
Allocated time: 13.1 hours
Complete 6 band (70-500um) observations of spectroscopically-confirmed cluster members in the Bullet Cluster have revealed a galaxy population with unexpectedly warm dust (T>40K) for sub-LIRG sources. No field sources of similar luminosity, at any redshift, have comparable dust temperatures, indicating that such warm dust may at least be preferentially located in dense environments. There are currently two problems testing this hypothesis more rigorously: (1) constraining the temperature of warm dust at z~0.3, requires 70um data, as the peak moves blue-ward of the range adequately constrained by 100 and 160um alone; (2) 70um observations of massive clusters are rare, as Spitzer/MIPS was only sensitive enough to probe the nearest poor cluster environments, and Herschel programs have tended to opt for only the 100um filter configuration. Indeed, the Bullet Cluster remains one of the only massive clusters with deep 6-band Herschel photometry.
Here we propose deep 70um PACS observations of four clusters from the Herschel Lensing Survey (HLS): A68, A2744, AS1063, A851 (26.1 hours in total). This sample has the advantage of existing deep 5-band Herschel data, as well 5-band Spitzer IRAC/MIPS coverage and a wealth of optical ancillary data, including 1000s of spectroscopic redshifts. The systems cover a range of cluster morphologies (multi-component mergers to relaxed systems). The observations will allow us to: (1) constrain the characteristic dust temperature of cluster galaxies with unusually warm dust; (2) search for similarly warm dust in foreground field galaxies to assess whether the phenomenon is a product of environment; (3) better constrain the FIR luminosity for all Herschel sources, using 70um to sample the mid-IR gap between 24 and 100um, and the deeper 160um data to increase the number of SPIRE sources detected by PACS; (4) improve Herschel-based photometric redshifts for high-z lensed sources.
Lead Scientist: Tim Rawle
Allocated time: 26.1 hours
Gravitational lensing offers a powerful method of observing intrinsically faint, high-redshift sources. Until recently, only a handful of FIR-bright, lensed galaxies have been discovered. Most of these are magnified by a single foreground galaxy, which can be difficult to disentangle spatially. Cluster lensing, on the other hand, offers the ability to accurately reconstruct the morphology of the magnified source. The SPIRE Snapshot Survey (currently 78 clusters observed from a sample of ~280) has so far discovered 10 bright, high redshift (z>1.5) sources. These include a confirmed z=4.69 source with 4 identified optical images coincident with submm peaks, and a z=2.4 source with a 500um flux of 230 mJy. We propose PACS 100 and 160 um observations for the 10 sources (total observing time of 7.2 hours), to complete the FIR SED and enable us to accurately constrain the FIR luminosity and dust properties.
Lead Scientist: Tim Rawle
Allocated time: 7.2 hours
Witnessing the assembly of a massive cluster at z = 1: a microcosm for the SFR-density relation of the universe
We request deep PACS imaging observations of a rare merging super-cluster, RCS2319, at z = 0.9. This system is projected to form a 10^15 MSun cluster by z = 0.2, but has been caught in the process of its assembly through the merging of three massive clusters. At this redshift star formation has migrated to higher density regions than seen locally, but it is not clear if the peak of the star-formation-rate-density relation has yet reached cluster core densities. This systems can directly answer this question by probing a wide range of galaxy environments and densities within a single uniform data set. We have assembled an extensive catalog of spectroscopy and imaging which allows us to trace the galaxy density and substructure within RCS2319 and control for galaxy mass, but lack the infrared measurements necessary for accurate star formation rates that Herschel alone can provide. With these measurements we will characterize the role of the environment in stellar mass assembly, investigate the hierarchical processes of merging and infall through which massive clusters form, and elucidate the cluster-specific mechanisms which regulate galaxy evolution within dense environments.
Lead Scientist: Tracy Webb
Allocated time: 58.8 hours
We propose an experiment to search for signatures of rapid growth of galaxies and AGNs in a sample of three z>2 proto-clusters. These environments are exceptionally rare, pre-virialised regions corresponding to peaks in the matter density field, located at the nodes of large-scale (>10-Mpc) filamentary structures. They are the best candidates for the progenitors of the most massive clusters of galaxies (~10^15-Msun) today. We pay special attention to an unusual class of object, preferentially located in proto-clusters: Lyman alpha blobs (LABs) - 100-kpc scale luminous emission-line gas nebulae. Some LABs show signatures of recent galaxy-galaxy mergers/interactions, are often host to luminous continuum sources, and many have evidence of gas inflows/outflows in their emission-line morphology. A significant fraction of LABs have embedded galaxies detected at X-ray, mid-infrared, and/or sub-mm wavelengths, suggesting possible rapid growths of the galaxies and AGNs in proto-cluster regions. Are the proto-cluster systems more obscured than galaxies in the field? Are the protocluster systems growing more rapidly? By mapping these proto-clusters with SPIRE, we will: (1) measure SFRs in sub-mm (rest-frame FIR) for the galaxies and AGNs in the proto-clusters, and determine how much star formation is obscured (when compared to UV estimate) and (2) determine SSFRs for the galaxies and AGNs in the proto-clusters, and see how they compare to field galaxies at z=2-3. This program will deliver fundamental information on the growth of galaxies and super-massive black holes in the densest regions of the Universe at high-redshift, and provide valuable insight into the astrophysical processes that establish the trends linking galaxy properties and their environments.
Lead Scientist: Yuichi Matsuda
Allocated time: 11.9 hours
Mission elapsed time:
14th May 2009 14:12:02 BST
Distance from Earth:
RA and DEC:
Updated on 22-May-2013
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